feat(web): restore last org + agent + thread on reopen

[pedrofrxncx]

Summary

When you reopen Studio, it now opens where you left off — same org, same agent, same thread — instead of dropping you on the org home.

Org restore already existed (lastOrgSlug). This adds the missing pieces: the agent (virtualmcpid) and the thread (taskId).

How it works

• lib/last-location.ts (new) — a tiny localStorage-backed { org, taskId, virtualmcpid } record with save / read / clear.
• Persist — unifiedChatRoute.beforeLoad saves the location on every navigation to a thread. defaultPreload is off, so this only fires on real navigation (not hover-preload).
• Restore — homeRoute.beforeLoad (path /) redirects to the saved /$org/$taskId?virtualmcpid=… before the existing lastOrgSlug fast path. The read is synchronous, so cold entry stays instant (no added network round-trip). autosend and other transient search params are intentionally not restored, so reopening never re-sends a message.
• Self-heal — OrgAccessGate now also clears last-location (not just lastOrgSlug) when the restored org turns out to be stale, so a revoked-access org can't loop back to itself. A stale taskId self-heals via useEnsureTask (re-fetch from server; idempotent create only if it genuinely doesn't exist).

Affected areas

• apps/mesh/src/web/index.tsx — restore + persist hooks
• apps/mesh/src/web/lib/last-location.ts — new helper
• apps/mesh/src/web/lib/localstorage-keys.ts — new lastLocation key
• apps/mesh/src/web/components/org-access-gate.tsx — loop-safe self-heal

Testing

• bun run --cwd=apps/mesh check — no type errors in the touched files.
• bun run lint / bun run fmt — clean (the 2 lint warnings are pre-existing in packages/sandbox).
• Not yet run live — needs a manual pass:
  1. Open a thread under an agent, send a message.
  2. Close the tab / quit the PWA, reopen at /.
  3. Expect to land back in that same thread (org + agent + thread), with no auto-resend.
  4. Lose access to that org (or delete it) → reopening should bounce cleanly to a valid org, not loop or dead-end.

Note: this changes the default landing for returning users from the org home to their last thread — which is the intent of the request.

🤖 Generated with Claude Code

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Summary by cubic

On reopen, Studio now restores where you left off: same org, agent (virtualmcpid), and thread (taskId). Uses a single last-location source of truth, won’t undo a recent org switch, and avoids auto-resend and extra network on cold entry.

• New Features

  • Added a last-location localStorage helper (save/read/clear).
  • Record org via orgLayout.beforeLoad; add taskId/virtualmcpid via unifiedChatRoute.beforeLoad.
  • Restore on “/” via homeRoute.beforeLoad from last-location (thread first, else org); fall back to lastOrgSlug only if absent.
  • Self-heal: stale taskId is recovered by useEnsureTask.

• Bug Fixes

  • Guarded null editor in the Tiptap content-sync effect to prevent a startup crash when restoring into a thread.
  • OrgAccessGate: show not-found/no-access for deliberately bad orgs; only bounce to “/” when the visit came from the cached lastOrgSlug. Clear a matching last-location so it won’t be restored.

^{Written for commit fc56bf7. Summary will update on new commits.}