fix: prevent false empty states during stack hydration (#1659)

* fix: prevent false empty states during stack hydration

Only show confirmed-empty UI after successful stack, status, and container
fetches. Distinguish loading and recoverable error states in the sidebar,
dashboard, and container health panel.

* fix: arbitrate overlapping stack status and container fetches

Prevent older dashboard status and same-owner container responses from overwriting newer load state after concurrent poll, invalidation, retry, or lifecycle refresh.

* fix: do not let soft status polls starve slow foreground loads

Skip soft /stacks/statuses poll and invalidation while a statuses request is already in flight so a deferred foreground hydration can still commit after the ten-second cadence.

* fix(stacks): surface recoverable errors for confirmed-empty soft failures

Sidebar and dashboard soft (background) refresh failures after a
confirmed-empty state silently kept showing the empty/adopt prompt
instead of a recoverable error, since only the error message was set
without flipping the load status. Also reject malformed non-array
/stacks responses instead of coercing them into a confirmed-empty list,
and drop malformed per-stack status entries before they reach the
dashboard table, which previously crashed the entire app on a null
entry.

* fix(stacks): close two review-found gaps in the load-failure fix

A non-empty stack-statuses map where every entry failed validation was
still committed as a confirmed-empty success; it now surfaces as a
recoverable error instead, and dropped entries are logged. The sidebar's
background-failure helper also checked a stale closure snapshot of the
file list, which could wipe a list that had just loaded non-empty in the
same attempt if the follow-up statuses fetch then failed; it now tracks
the freshest committed list for that decision. Also collapses two refs
tracking dashboard status-map emptiness into one.

frontend/src/components/EditorLayout.tsx

@@ -105,6 +105,8 @@ export default function EditorLayout() {
     envFiles,
     selectedEnvFile,
     containers,
+    containersLoadStatus,
+    containersLoadError,
     activeTab, setActiveTab,
     logsMode, setLogsMode,
     gitSourceOpen, setGitSourceOpen,
@@ -616,6 +618,9 @@ export default function EditorLayout() {
       stackName={stackName}
       isDarkMode={isDarkMode}
       containers={containers}
+      containersLoadStatus={containersLoadStatus}
+      containersLoadError={containersLoadError}
+      onRetryContainersLoad={() => { void stackActions.retryContainersLoad(); }}
       containerStats={containerStats}
       containerStatsError={containerStatsError}
       content={content}