feat(search): add global Ctrl+K command palette (#711)

* feat(search): add global command palette with cross-node stacks

Press Ctrl+K from anywhere to open a search palette that jumps to
pages, switches nodes, or opens stacks on any online node in the
fleet. Trigger lives as an icon in the top bar. Replaces the former
sidebar-scoped Ctrl+K handler.

The cross-node stack search fan-out is extracted into a shared hook
so the sidebar and palette stay in sync on the same debounce +
abort shape.

* fix(search): drop render-time ref write and effect-based query reset

Replace `nodesRef.current = nodes` during render with direct use of
`nodes` in the stack select callback, and fold the query-reset logic
into a single `onOpenChange` handler so it no longer runs via an
effect. Both changes resolve react-hooks rule violations that broke
frontend lint in CI.

frontend/src/hooks/useCrossNodeStackSearch.ts

@@ -0,0 +1,98 @@
+import { useEffect, useRef, useState } from 'react';
+import { useNodes } from '@/context/NodeContext';
+import { fetchForNode } from '@/lib/api';
+
+export type StackStatus = 'running' | 'exited' | 'unknown';
+
+export interface StackStatusInfo {
+    status: StackStatus;
+}
+
+export interface StackHit {
+    nodeId: number;
+    nodeName: string;
+    file: string;
+    status: StackStatus;
+}
+
+interface Options {
+    query: string;
+    enabled: boolean;
+    excludeNodeId?: number;
+}
+
+const DEBOUNCE_MS = 250;
+
+export function useCrossNodeStackSearch({ query, enabled, excludeNodeId }: Options) {
+    const { nodes } = useNodes();
+    const [hits, setHits] = useState<StackHit[]>([]);
+    const [loading, setLoading] = useState(false);
+
+    // Ref avoids re-running the effect on every NodeContext status tick
+    const nodesRef = useRef(nodes);
+    nodesRef.current = nodes;
+
+    useEffect(() => {
+        const q = query.trim().toLowerCase();
+        if (!enabled || !q) {
+            setHits([]);
+            setLoading(false);
+            return;
+        }
+        const targets = nodesRef.current.filter(
+            n => n.status !== 'offline' && n.id !== excludeNodeId,
+        );
+        if (targets.length === 0) {
+            setHits([]);
+            return;
+        }
+        const controller = new AbortController();
+        const timer = setTimeout(async () => {
+            setLoading(true);
+            try {
+                const perNode = await Promise.all(targets.map(async (node) => {
+                    try {
+                        const [listRes, statusRes] = await Promise.all([
+                            fetchForNode('/stacks', node.id, { signal: controller.signal }),
+                            fetchForNode('/stacks/statuses', node.id, { signal: controller.signal }),
+                        ]);
+                        if (!listRes.ok) return [] as StackHit[];
+                        const rawList = await listRes.json();
+                        const files: string[] = Array.isArray(rawList) ? rawList : [];
+                        const statuses: Record<string, StackStatus> = {};
+                        if (statusRes.ok) {
+                            const raw = await statusRes.json();
+                            for (const [key, val] of Object.entries(raw)) {
+                                if (typeof val === 'string') {
+                                    statuses[key] = val as StackStatus;
+                                } else if (val && typeof val === 'object' && 'status' in val) {
+                                    statuses[key] = (val as StackStatusInfo).status;
+                                }
+                            }
+                        }
+                        return files
+                            .filter(f => f.toLowerCase().includes(q))
+                            .map<StackHit>(file => ({
+                                nodeId: node.id,
+                                nodeName: node.name,
+                                file,
+                                status: statuses[file] ?? 'unknown',
+                            }));
+                    } catch {
+                        return [] as StackHit[];
+                    }
+                }));
+                if (controller.signal.aborted) return;
+                setHits(perNode.flat());
+            } finally {
+                if (!controller.signal.aborted) setLoading(false);
+            }
+        }, DEBOUNCE_MS);
+        return () => {
+            clearTimeout(timer);
+            controller.abort();
+        };
+    }, [enabled, query, excludeNodeId]);
+
+    return { hits, loading };
+}