fix(app): refresh artifact panel when agent modifies the open file

[PriyeshPandey2000]

Summary

• Artifact preview panel showed stale content after the agent modified the open file — only a full app restart cleared it.
• isSameTranscriptArtifactTargets compared targets only by id, ignoring mtime changes, so the Zustand store never propagated file updates to the panel.
• staleTime: Infinity with no cache invalidation meant React Query served the initial fetch indefinitely.
• Fix: include target.updatedAt (file mtime already returned by resolveArtifacts) in the React Query cache key and in the transcript-targets equality check. Add gcTime: 0 so close/reopen also fetches fresh.

Why

When the agent writes a file, the server already returns the updated mtime via resolveArtifacts. That signal existed in the pipeline but was never used to bust the cache or notify the panel.

Issue

Closes #2924

Scope

• apps/app/src/react-app/domains/session/artifacts/artifact-panel.tsx — add target.updatedAt to query key and setQueryData key; add gcTime: 0
• apps/app/src/react-app/domains/session/panel/panel-tab-store.ts — include updatedAt in isSameTranscriptArtifactTargets

Testing

Ran

• pnpm typecheck — pass

Manual

1. Ask agent to create a .md file, open preview panel, ask agent to modify it — panel updates automatically ✓
2. Close preview panel while agent modifies file, reopen — shows latest content ✓
3. Edit file manually via in-panel editor and save — content correct after save ✓
4. Open non-markdown artifact (image, PDF) — no regression ✓

Evidence

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
openwork-landing	Ready	Preview, v0	Jul 30, 2026 8:38am

1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
openwork-diagnostics	Skipped		Jul 30, 2026 8:38am

[vercel]

@PriyeshPandey2000 is attempting to deploy a commit to the Different AI Team on Vercel.

A member of the Team first needs to authorize it.

[PriyeshPandey2000]

Hi @benjaminshafii , would appreciate a review when you get a chance. Happy to address any feedback.

[reachjalil]

Rebased the existing PR head onto current dev at
986e618c5d752ba4dd0fc007c94b4811c651c0fd while preserving the original
single-commit patch and authorship.

Current rebased head: 1f33e2d76c890377e5164f4c5edc64d9c004df86.

Validation on the rebased head:

• pnpm --filter @openwork/app test — 534 passed, 0 failed
• pnpm --filter @openwork/app typecheck — passed
• git diff --check — passed

The three Vercel failures are fork authorization statuses rather than code/test
failures. This PR remains open and unmerged for Jalil's review.

[reachjalil]

Thanks @PriyeshPandey2000 — clean, focused fix for stale artifact previews. Verified against current dev. Appreciate the contribution!