feat(app): let the conversation lead the Goal Chat view

[huangruiteng]

Stacked on #5071. The Goal conversation is now the main content of the Goal Chat view. Background machinery no longer stacks up above it.

Delivery brief

• Goal/source: The App conversation RFC (docs/architecture/rfcs/app-conversation-and-async-inbox-v0.md) asks for the conversation to dominate the view, with delegation and returns shown inline.
• Current gap: Opening a busy Goal's Chat showed a column of cards before any message: every scheduled monitor and heartbeat, routine runs, and every draft proposal. Drafts were labelled with raw protocol strings such as monitor.create · ready.
• Observable result:
  • Scheduled checks, heartbeats and routine runs fold into one 后台工作 / Background work line, for example 4 个定时任务已启用 · 1 次执行已结束.
  • Drafts use owner language, for example 新定时检查 · 待你确认 / New scheduled check · Awaiting you. Only the newest draft awaiting the owner stays open; the others fold into 另有 N 个待确认提议.
• Owning boundary: presentation only (channel-timeline.tsx). No change to the action, proposal or schedule contracts.

What stays visible

These stay visible on purpose, and no text-based inference decides that something is safe to hide:

• items that need you;
• waiting, interrupted and failed runs;
• applying, applied, failed and stale proposals;
• the gated (needs-authorization) history, which keeps its existing fold.

Only proposals whose status is ready fold behind the newest one.

Behavior change disclosure

• Schedule rows are no longer in the main timeline by default. They open from the Background work fold, and their drawers and actions are unchanged.
• The proposal row label no longer shows the raw action kind. The kind moves to data-action-kind for tooling and tests. The typed-actions, steward-journey and team-plan scenarios now select by that attribute and assert the owner-facing label.

Entry points

• Frontend: changed.
• CLI and Lark: no change. They do not render the App timeline.

Validation

• tsc --noEmit: passed.
• npm run build, including the packaged chat bundle: passed.
• Personal workspace browser suite, all 17 scenarios: passed in development and in packaged mode.
• typed-actions now asserts that a schedule is hidden until Background work is opened, then drives the schedule drawer actions (run now, pause, edit, stop) from the fold.

Future-facing pass

Applied: kind and status labels come from one i18n map (proposal.kind.*, proposal.status.*) instead of string concatenation. Deferred: delegation and returned results inline in the conversation (async inbox) will be the next slice.

First-screen gate

This changes the Goal Chat first viewport. The owner reviews before/after screenshots before merge; leave the merge to the maintainer.