fix: make Home meeting reveal/delete robust to stale row paths

[r3dbars]

Summary

Fixes the per-meeting overflow (⋯) menu on the Home dashboard. The reveal-in-Finder and delete actions failed in the field because the row holds the file URLs captured when the dashboard was last scanned, and background work moves those files afterwards:

• the post-save restyle renames a meeting transcript (and its audio/<stem>_audio/ bundle)
• retained audio is recompressed from WAV → M4A after save

NSWorkspace.activateFileViewerSelecting(_:) silently no-ops on a missing path — that is the "Show … in Finder does nothing / works on one machine but not another" report. "Delete meeting" shared the root cause: a stale path means the deletion plan removes nothing, the row is optimistically hidden, then reappears on the next refresh with no explanation.

Context: PRs #1126 / #1131 fixed the delete alert plumbing (the confirmation now appears and fires deleteMeeting). The delete data layer (HomeMeetingDeletion) is solid and well-tested. This PR addresses the remaining real-world failure mode — path staleness — and makes every reveal action fail loud instead of silent.

Per-action findings

Action	Status	Finding
Show transcript in Finder	Fixed	Raw activateFileViewerSelecting([transcriptURL]) silently no-ops when the transcript was renamed by the restyle after scan. Now resolved + falls back to the meetings folder + surfaces an error.
Show audio in Finder	Fixed	Same silent no-op; "works on one machine not another" = WAV→M4A recompression state differs. Now stem-rematches the recompressed file, falls back to the audio bundle dir, or errors.
Delete meeting	Hardened	Alert + data layer already correct (#1126/#1131 + HomeMeetingDeletionTests). Added: surface a failure when the delete removed nothing while the file is still on disk (stale path) instead of silently re-showing the row.
Run AI summary	By design (not broken)	Disabled when localMeetingSummaryUnavailableReason != nil: app busy, or the local-summary beta provider isn't set up (Gemma needs uv + enough memory, or Apple on-device model unavailable). Whole item is also behind the beta opt-in.
Re-transcribe with speaker ID	By design (not broken)	Only shown when retained split audio exists; disabled while the app is busy or when there's pending speaker review (which redirects to the review flow).
Report issue	Works	Opens the feedback sheet; unchanged.

Fix

• HomeArtifactRevealResolver (new, Foundation-pure, unit-tested): reveal files that still exist → else stem-rematch in the same directory (catches WAV→M4A) → else fall back to the enclosing folder → else .unavailable.
• Transcript, meeting-audio, and failed-meeting-audio reveal actions now route through a shared revealMeetingArtifact(...) helper that presents a failure alert when nothing can be revealed.
• deleteMeeting surfaces a failure on a no-op stale delete.

Tests

• HomeArtifactRevealResolverTests — direct hit, partial existence, WAV→M4A stem rematch, renamed-transcript directory fallback, both unavailable cases. (6 cases, passing.)
• Source-contract guards in UIAutomationSurfaceContractTests and RepoCommandContractTests pin the resilient wiring.
• Full fast suite: 5424 passed, 0 failed. App builds clean (build.sh --no-open).

⚠️ Manual proof still needed

Reveal and delete are real-app behaviors that tests alone cannot prove. On a running build, on a real meeting, a human should click:

1. Show transcript in Finder → Finder reveals the .md (or its folder if renamed).
2. Show audio in Finder → Finder reveals the retained audio (force a WAV→M4A recompression case if possible).
3. Delete meeting → confirm → the row disappears and stays gone after the list refreshes; the on-disk .md, .summary.md, and audio/<stem>_audio/ are removed.
4. Trigger a stale-path case (rename/move a transcript outside the app, then use the still-open row) → each action should show an error alert, never a dead click.

Notes

• App is not sandboxed (com.apple.security.app-sandbox = false), so this was never a security-scoped-bookmark problem.
• Draft — do not merge.

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