refactor(frontend): migrate diff dialogs to Modal chrome (D-5) (#909)

* refactor(frontend): extend Modal size system with wide variant

Adds 'wide' (max-w-5xl w-[95vw]) to ModalSize for dialogs that render
Monaco DiffEditor side-by-side, which need ~1024px to display both panels
clearly. The existing 'xl' cap at max-w-xl (576px) is too narrow for that
use case.

* refactor(frontend): migrate ComposeDiffPreviewDialog to Modal chrome (D-5)

Replaces raw Dialog/DialogHeader/DialogFooter with Modal size="wide",
ModalHeader, and ModalFooter. Kicker carries the stack name and file type
context; title is the file name (accessible dialog name for tests). Footer
hint reuses the existing "ON DISK → UNSAVED" label via the hint prop.

* refactor(frontend): migrate GitSourceDiffDialog to Modal chrome (D-5)

Replaces Dialog + nested AlertDialog with Modal size="wide", ModalHeader,
ModalFooter, and ConfirmModal. Kicker is "GIT · PULL PREVIEW"; title is
the stack name. Short SHA moves to the sr-only description. The "Deploy
after apply" checkbox in the footer hint slot uses normal-case and
tracking-normal on the Label to prevent KICKER_CLASS uppercase/tracking
from being inherited. The overwrite confirmation uses ConfirmModal with
variant="destructive" (rose rail) since it replaces local file content.

frontend/src/components/stack/GitSourceDiffDialog.tsx

@@ -1,8 +1,7 @@
 import { useState, Suspense } from 'react';
 import { DiffEditor } from '@/lib/monacoLoader';
-import { AlertTriangle, GitBranch, Loader2 } from 'lucide-react';
-import { Dialog, DialogContent, DialogHeader, DialogTitle, DialogDescription, DialogFooter } from '@/components/ui/dialog';
-import { AlertDialog, AlertDialogAction, AlertDialogCancel, AlertDialogContent, AlertDialogDescription, AlertDialogFooter, AlertDialogHeader, AlertDialogTitle } from '@/components/ui/alert-dialog';
+import { AlertTriangle, Loader2 } from 'lucide-react';
+import { Modal, ModalHeader, ModalFooter, ConfirmModal } from '@/components/ui/modal';
 import { Tabs, TabsList, TabsTrigger, TabsHighlight, TabsHighlightItem } from '@/components/ui/tabs';
 import { Button } from '@/components/ui/button';
 import { Checkbox } from '@/components/ui/checkbox';
@@ -72,79 +71,73 @@ export function GitSourceDiffDialog({
 
   return (
     <>
-      <Dialog open={open} onOpenChange={onOpenChange}>
-        <DialogContent className="max-w-5xl w-[95vw] p-0 gap-0">
-          <DialogHeader className="px-6 pt-6 pb-4 border-b border-glass-border">
-            <DialogTitle className="flex items-center gap-2">
-              <GitBranch className="w-4 h-4" strokeWidth={1.5} />
-              <span>Review update for</span>
-              <span className="font-mono tabular-nums">{stackName}</span>
-              <span className="font-mono tabular-nums text-xs text-stat-subtitle">@{shortSha}</span>
-            </DialogTitle>
-            <DialogDescription className="sr-only">
-              Review the diff between the current on-disk stack files and the incoming Git commit.
-            </DialogDescription>
-          </DialogHeader>
+      <Modal size="wide" open={open} onOpenChange={onOpenChange}>
+        <ModalHeader
+          kicker="GIT · PULL PREVIEW"
+          title={stackName}
+          description={`Incoming commit ${shortSha}. Review the diff between the current on-disk stack files and the incoming Git commit.`}
+        />
 
-          <div className="px-6 pt-4 space-y-3">
-            {!pull.validation.ok && (
-              <div className="flex items-start gap-2 rounded-md border border-destructive/30 bg-destructive/10 px-3 py-2 text-xs text-destructive">
-                <AlertTriangle className="w-4 h-4 shrink-0 mt-0.5" strokeWidth={1.5} />
-                <div>
-                  <p className="font-medium">Incoming compose failed validation</p>
-                  <pre className="font-mono text-[11px] whitespace-pre-wrap mt-1">{pull.validation.error}</pre>
-                </div>
+        <div className="px-6 pt-4 space-y-3">
+          {!pull.validation.ok && (
+            <div className="flex items-start gap-2 rounded-md border border-destructive/30 bg-destructive/10 px-3 py-2 text-xs text-destructive">
+              <AlertTriangle className="w-4 h-4 shrink-0 mt-0.5" strokeWidth={1.5} />
+              <div>
+                <p className="font-medium">Incoming compose failed validation</p>
+                <pre className="font-mono text-[11px] whitespace-pre-wrap mt-1">{pull.validation.error}</pre>
               </div>
-            )}
-            {pull.hasLocalChanges && (
-              <div className="flex items-start gap-2 rounded-md border border-warning/30 bg-warning/10 px-3 py-2 text-xs text-warning">
-                <AlertTriangle className="w-4 h-4 shrink-0 mt-0.5" strokeWidth={1.5} />
-                <div>
-                  <p className="font-medium">Local edits detected on disk</p>
-                  <p className="mt-0.5">Applying will overwrite changes that differ from the last applied commit.</p>
-                </div>
-              </div>
-            )}
-
-            {envAvailable && (
-              <Tabs value={diffTab} onValueChange={(v) => setDiffTab(v as 'compose' | 'env')}>
-                <TabsList>
-                  <TabsHighlight className="rounded-md bg-glass-highlight" transition={springs.snappy}>
-                    <TabsHighlightItem value="compose">
-                      <TabsTrigger value="compose">compose.yaml</TabsTrigger>
-                    </TabsHighlightItem>
-                    <TabsHighlightItem value="env">
-                      <TabsTrigger value="env">.env</TabsTrigger>
-                    </TabsHighlightItem>
-                  </TabsHighlight>
-                </TabsList>
-              </Tabs>
-            )}
-          </div>
-
-          <div className="px-6 pb-4 pt-3">
-            <div className="h-[55vh] border border-glass-border rounded-md overflow-hidden">
-              <Suspense fallback={<div className="w-full h-full" aria-busy="true" />}>
-                <DiffEditor
-                  height="100%"
-                  language={effectiveTab === 'compose' ? 'yaml' : 'ini'}
-                  theme={isDarkMode ? 'vs-dark' : 'vs'}
-                  original={currentValue}
-                  modified={incomingValue}
-                  options={{
-                    readOnly: true,
-                    renderSideBySide: true,
-                    minimap: { enabled: false },
-                    scrollBeyondLastLine: false,
-                    fontFamily: "'Geist Mono', monospace",
-                    fontSize: 12,
-                  }}
-                />
-              </Suspense>
             </div>
-          </div>
+          )}
+          {pull.hasLocalChanges && (
+            <div className="flex items-start gap-2 rounded-md border border-warning/30 bg-warning/10 px-3 py-2 text-xs text-warning">
+              <AlertTriangle className="w-4 h-4 shrink-0 mt-0.5" strokeWidth={1.5} />
+              <div>
+                <p className="font-medium">Local edits detected on disk</p>
+                <p className="mt-0.5">Applying will overwrite changes that differ from the last applied commit.</p>
+              </div>
+            </div>
+          )}
 
-          <DialogFooter className="px-6 py-4 border-t border-glass-border flex flex-row items-center justify-between sm:justify-between gap-4">
+          {envAvailable && (
+            <Tabs value={diffTab} onValueChange={(v) => setDiffTab(v as 'compose' | 'env')}>
+              <TabsList>
+                <TabsHighlight className="rounded-md bg-glass-highlight" transition={springs.snappy}>
+                  <TabsHighlightItem value="compose">
+                    <TabsTrigger value="compose">compose.yaml</TabsTrigger>
+                  </TabsHighlightItem>
+                  <TabsHighlightItem value="env">
+                    <TabsTrigger value="env">.env</TabsTrigger>
+                  </TabsHighlightItem>
+                </TabsHighlight>
+              </TabsList>
+            </Tabs>
+          )}
+        </div>
+
+        <div className="px-6 pb-4 pt-3">
+          <div className="h-[55vh] border border-glass-border rounded-md overflow-hidden">
+            <Suspense fallback={<div className="w-full h-full" aria-busy="true" />}>
+              <DiffEditor
+                height="100%"
+                language={effectiveTab === 'compose' ? 'yaml' : 'ini'}
+                theme={isDarkMode ? 'vs-dark' : 'vs'}
+                original={currentValue}
+                modified={incomingValue}
+                options={{
+                  readOnly: true,
+                  renderSideBySide: true,
+                  minimap: { enabled: false },
+                  scrollBeyondLastLine: false,
+                  fontFamily: "'Geist Mono', monospace",
+                  fontSize: 12,
+                }}
+              />
+            </Suspense>
+          </div>
+        </div>
+
+        <ModalFooter
+          hint={
             <div className="flex items-center gap-2">
               <Checkbox
                 id="git-source-deploy-after"
@@ -152,60 +145,57 @@ export function GitSourceDiffDialog({
                 onCheckedChange={(checked) => setDeployAfter(checked === true)}
                 disabled={applying || !pull.validation.ok}
               />
-              <Label htmlFor="git-source-deploy-after" className="text-xs cursor-pointer">
+              <Label
+                htmlFor="git-source-deploy-after"
+                className="text-xs normal-case tracking-normal cursor-pointer"
+              >
                 Deploy after apply
               </Label>
             </div>
-            <div className="flex items-center gap-2">
-              <Button
-                variant="outline"
-                size="sm"
-                onClick={() => onDismiss()}
-                disabled={applying}
-              >
-                Dismiss
-              </Button>
-              <Button
-                size="sm"
-                onClick={handleApplyClick}
-                disabled={applying || !pull.validation.ok}
-              >
-                {applying ? (
-                  <>
-                    <Loader2 className="w-4 h-4 mr-1.5 animate-spin" strokeWidth={1.5} />
-                    Applying...
-                  </>
-                ) : (
-                  'Apply'
-                )}
-              </Button>
-            </div>
-          </DialogFooter>
-        </DialogContent>
-      </Dialog>
-
-      <AlertDialog open={confirmOpen} onOpenChange={setConfirmOpen}>
-        <AlertDialogContent>
-          <AlertDialogHeader>
-            <AlertDialogTitle>Overwrite local edits?</AlertDialogTitle>
-            <AlertDialogDescription>
-              The on-disk stack files differ from the last applied commit. Applying this pull will replace them with the incoming content.
-            </AlertDialogDescription>
-          </AlertDialogHeader>
-          <AlertDialogFooter>
-            <AlertDialogCancel disabled={applying}>Cancel</AlertDialogCancel>
-            <AlertDialogAction
-              onClick={async () => {
-                setConfirmOpen(false);
-                await apply();
-              }}
+          }
+          secondary={
+            <Button
+              variant="outline"
+              size="sm"
+              onClick={() => onDismiss()}
               disabled={applying}
             >
-              Overwrite and apply
-            </AlertDialogAction>
-          </AlertDialogFooter>
-        </AlertDialogContent>
-      </AlertDialog>
+              Dismiss
+            </Button>
+          }
+          primary={
+            <Button
+              size="sm"
+              onClick={handleApplyClick}
+              disabled={applying || !pull.validation.ok}
+            >
+              {applying ? (
+                <>
+                  <Loader2 className="w-4 h-4 mr-1.5 animate-spin" strokeWidth={1.5} />
+                  Applying...
+                </>
+              ) : (
+                'Apply'
+              )}
+            </Button>
+          }
+        />
+      </Modal>
+
+      <ConfirmModal
+        open={confirmOpen}
+        onOpenChange={setConfirmOpen}
+        variant="destructive"
+        kicker="GIT · LOCAL CHANGES"
+        title="Overwrite local edits?"
+        description="The on-disk stack files differ from the last applied commit. Applying this pull will replace them with the incoming content."
+        confirmLabel="Overwrite and apply"
+        confirming={applying}
+        onConfirm={async () => {
+          setConfirmOpen(false);
+          await apply();
+        }}
+      />
     </>
   );
 }