feat(archive): Add undo button to task archived toast

[charlesvien]

Problem

Archiving a task is easy to trigger by accident, and the only way to reverse it is to open the Archived tasks page and unarchive from there. There is no quick in-place undo.

Changes

1. Add an Undo action to the "Task archived" toast that restores the task in place
2. Reuse the existing useUnarchiveTask().restore() flow, no new API or server changes
3. On the rare branch-not-found case, auto-retry with branch recreation and surface a toast error only on hard failure
4. Add a duration option to toast.success and keep the archived toast up ~8s for reaction time

How did you test this?

• pnpm --filter @posthog/ui typecheck passes
• pnpm exec biome lint on both changed files is clean (also enforced by the pre-commit hook)
• Manual in-app verification (archive then Undo from the sidebar) not yet run; the Undo reuses the same restore path the Archived tasks page already uses

Automatic notifications

• Publish to changelog?
• Alert Sales and Marketing teams?

[charlesvien]

• feat(archive): Add undo button to task archived toast #2665 👈 (View in Graphite)
• main

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[github-actions]

React Doctor found no issues in the changed files. 🎉

_{Reviewed by React Doctor for commit bb14f24.}

[greptile-apps]

Prompt To Fix All With AI

Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 1
packages/ui/src/features/archive/useArchiveTask.ts:181-183
After the `recreateBranch` retry, if `restore` still returns `"branch-not-found"`, the condition `outcome.kind === "error"` is false so no toast is shown — the undo silently fails with no user feedback. The `RestoreOutcome` union has exactly three variants (`"restored"`, `"branch-not-found"`, `"error"`), so a `"branch-not-found"` result after the retry needs to be treated as an error for the user.

```suggestion
  if (outcome.kind === "error") {
    toast.error(`Failed to restore task: ${outcome.message}`);
  } else if (outcome.kind === "branch-not-found") {
    toast.error(`Failed to restore task: branch '${outcome.branchName}' not found`);
  }
```

_{Reviews (1): Last reviewed commit: "add undo button to task archived toast" | Re-trigger Greptile}

[stamphog]

The unresolved bot comment identifies a real silent-failure bug: after the recreateBranch retry, if restore still returns "branch-not-found", neither the "branch-not-found" branch (already consumed) nor the "error" branch applies, so the undo silently fails with no user feedback. The current diff leaves this gap unaddressed.

[github-actions]

The bot-flagged silent-failure path is handled in the current code: outcome is let-reassigned after the retry, and the subsequent block re-checks outcome.kind === "branch-not-found" to show an error toast. Both bot reviews target an older commit and the concern is addressed. All other changes are additive and low-risk.

New commits pushed (delta classified non_trivial_delta) — stamphog approval dismissed; re-review running automatically.

[github-actions]

The bot-flagged silent-failure path is fully addressed in the current code — outcome is let-reassigned after the retry and the subsequent branch-not-found check emits an error toast. Tests explicitly cover the retry-still-fails case. All changes are additive UI-layer additions with no boundary violations.

New commits pushed (delta classified non_trivial_delta) — stamphog approval dismissed; re-review running automatically.

[github-actions]

No showstoppers. The previously flagged silent-failure path (branch still missing after retry) is correctly handled in the current code — outcome is reassigned after the retry and the subsequent branch-not-found check emits an error toast. Tests explicitly cover this case. The changes are additive UI-layer additions that respect package boundaries.

New commits pushed (delta classified non_trivial_delta) — stamphog approval dismissed; re-review running automatically.

[github-actions]

The previously flagged silent-failure path (branch still missing after retry) is correctly handled: after the retry, the code checks for "restored" and falls through to a unified error-toast block that covers both "branch-not-found" and "error" outcomes. Tests explicitly verify this case. All changes are additive UI-layer additions within @posthog/ui with no boundary violations.