fix(home): run quick actions inline with optimistic task insert

[k11kirky]

Problem

On the Home tab, clicking a quick action ("Fix CI", "Address comments", "Create PR", "Review with agent") navigated away — to the pending route and then the task-detail view — and gave no in-flight feedback on the button. The desired behaviour is to kick off the cloud task in place, show it immediately in the workstream's task list, and disable the button while it starts.

Changes

• Stay on Home. useRunWorkstreamAction no longer navigates to the pending or task-detail routes. It starts the cloud task, optimistically splices the new run into the workstream's task list (insertOptimisticTask), disables the trigger with a spinner while in flight (isPending threaded through useWorkstreamPresentation to the row / card / detail-panel buttons and overflow items), and fires a server snapshot refresh so the next poll reconciles. The offline / signed-out fallback still routes to the new-task screen.
• Quick-action tags. The action label flows end-to-end (TaskCreationInput.homeQuickActionLabel → saga → api-client home_quick_action body) so the server records which quick action started a run. The snapshot's HomeWorkstreamTask gains quickAction, rendered as a per-task chip in the detail panel and a glanceable "✨ Fix CI, …" indicator on the workstream row. The optimistic row is tagged immediately too.

Server half (grouping + home_quick_action persistence + quickAction in the snapshot) is in PostHog/posthog.

How did you test this?

• vitest run src/features/home — 36 passing, including new optimisticTask coverage (splice into the right workstream, no cross-workstream bleed, no duplicates, quick-action tagging).
• tsc --noEmit clean across @posthog/ui, @posthog/core, @posthog/shared, @posthog/api-client.
• biome check clean on all touched files.

I did test the app manually.

Automatic notifications

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

[github-actions]

React Doctor found no issues in the changed files. 🎉

_{Reviewed by React Doctor for commit 68799a0.}

[greptile-apps]

Prompt To Fix All With AI

Fix the following 3 code review issues. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 3
packages/ui/src/features/home/hooks/useRunWorkstreamAction.ts:75-107
**Per-instance `inFlightRef` doesn't guard across simultaneous row + detail panel mounts**

`HomeWorkstreamRow` (via `useWorkstreamPresentation`) and `HomeWorkstreamDetailPanel` both mount their own `useRunWorkstreamAction()` instance, each with an independent `inFlightRef` and `isPending` state. When the detail panel is open alongside the row, clicking the quick action in the row sets only the row's `inFlightRef.current = true` and `isPending = true`; the detail panel's guard is still `false`. A user can then immediately click the panel's action button and start a second task for the same workstream.

Before this PR, navigation away unmounted both surfaces, so races were impossible. The new stay-on-Home design keeps both mounted, making this a real double-submit path. Sharing state through a context or lifting `inFlightRef` to a workstream-keyed store (e.g. a `Map<workstreamId, boolean>` ref at a common ancestor) would close the gap.

### Issue 2 of 3
packages/ui/src/features/home/hooks/useRunWorkstreamAction.ts:197-199
`refreshHome` is the entire `useMutation` result object, which gets a new reference whenever mutation state transitions (idle → pending → settled). Including it in the `useCallback` dep array means `run` is recreated on every transition, which defeats memoisation and propagates new references through every `useWorkstreamPresentation` caller. `mutateAsync` is a stable reference in react-query v5 and is the correct dep here.

```suggestion
      queryClient,
      refreshHome.mutateAsync,
      getUserIntegrationIdForRepo,
```

### Issue 3 of 3
packages/ui/src/features/home/utils/optimisticTask.test.ts:40-71
**Prefer parameterised tests for `workstreamTaskFromTask`**

The four `workstreamTaskFromTask` cases are each a distinct input-to-output mapping and are a natural fit for `it.each`. Per the project's convention, parameterised tests are preferred; this block could be expressed as a single `it.each` table covering id, title, status, and quickAction across the four variants.

_{Reviews (1): Last reviewed commit: "fix(home): run quick actions inline with..." | Re-trigger Greptile}