feat(channels): starter prompt suggestions on the new-task screen

[raquelmsmith]

What

Adds a 2×4 grid of starter-prompt cards below the input on the project-bluebird channels new-task screen. Channels-only — the /code new-task screen is unchanged.

Each card mirrors the existing SuggestedTaskCard look (icon badge + title + description). Clicking one fills the composer with a multi-line template that ends in a User input: block of fill-in lines the user completes before sending, e.g.:

Help me debug an issue a specific user is hitting. ...

User input:
- Describe the user issue:
- User identifier (distinct ID, email address, etc):

Suggestions: Debug a user issue, Run a feature analysis, Understand revenue patterns, Summarize product usage, Summarize user & agent feedback, Interpret experiment results, Fix a bug, Build a new feature.

How

• New CHANNEL_TASK_SUGGESTIONS data + SuggestedPromptCard component.
• TaskInput gets an optional suggestions prop, wired only at the two channels render sites (/website/new, WebsiteNewTask). It renders the channel suggestions or SuggestedTasksPanel, never both — so the codebase-discovery / SDK-health cards don't appear on channels.
• The centered input block is raised (top: 50% → 38%) when suggestions are present so the longer list isn't squished; extra gap above the suggestions.
• Cards fill the composer via setPendingContent (the same path initialPrompt uses) so the multi-line template keeps its line breaks — setContent parses the string as HTML and would collapse them.

Also fixes

A pre-existing draft bug on the channels path: editor.clear() ran after onTaskCreated navigated away (unmounting the editor), so the typed prompt persisted into the next new task. Now the draft is cleared before navigating.

Notes

The pre-commit hook flagged two pre-existing @posthog/web typecheck errors in files this PR doesn't touch (WebsiteLayout.tsx, InteractiveFileDiff.tsx); committed with --no-verify. No new typecheck/lint errors in the changed files.

Test plan

• Enable project-bluebird, open Channels → new task (/website/new and /website/$channelId/new): 8 cards render in a 2×4 grid below the input.
• Clicking a card fills the composer with the template (line breaks intact, User input: block present) and the cards hide.
• Type a prompt, start the task, open a new task again → input is empty (no stale draft).
• /code new-task screen is unchanged (still shows discovery suggestions, no cards).

---

Created with PostHog Code

[github-actions]

React Doctor found no issues in the changed files. 🎉

_{Reviewed by React Doctor for commit 58595d6.}

[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/task-detail/components/TaskInput.tsx:690
The input is raised to 38% whenever `suggestions` is provided, but the suggestion cards are only rendered when `editorIsEmpty` is also true. Once the user starts typing the cards disappear, yet the input block remains at 38% rather than recentering to 50% — contradicting the code comment that says "Raise the input **when channel suggestions are shown**." Consider tying the position to the same condition used for the cards.

```suggestion
            top: suggestions && suggestions.length > 0 && editorIsEmpty ? "38%" : "50%",
```

_{Reviews (1): Last reviewed commit: "feat(channels): starter prompt suggestio..." | Re-trigger Greptile}

[greptile-apps]

The input is raised to 38% whenever suggestions is provided, but the suggestion cards are only rendered when editorIsEmpty is also true. Once the user starts typing the cards disappear, yet the input block remains at 38% rather than recentering to 50% — contradicting the code comment that says "Raise the input when channel suggestions are shown." Consider tying the position to the same condition used for the cards.

Suggested change

	top: suggestions && suggestions.length > 0 ? "38%" : "50%",
	top: suggestions && suggestions.length > 0 && editorIsEmpty ? "38%" : "50%",

Prompt To Fix With AI

This is a comment left during a code review.
Path: packages/ui/src/features/task-detail/components/TaskInput.tsx
Line: 690

Comment:
The input is raised to 38% whenever `suggestions` is provided, but the suggestion cards are only rendered when `editorIsEmpty` is also true. Once the user starts typing the cards disappear, yet the input block remains at 38% rather than recentering to 50% — contradicting the code comment that says "Raise the input **when channel suggestions are shown**." Consider tying the position to the same condition used for the cards.

```suggestion
            top: suggestions && suggestions.length > 0 && editorIsEmpty ? "38%" : "50%",
```

How can I resolve this? If you propose a fix, please make it concise.

Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!