feat(app): show needs you, pick back up, and team pulse on the project dashboard - #471

Part of #36. The project dashboard gets three sections built from listings, attention hints, the lobby, and the owner's gh account. Nothing new is stored durably. The greeting, the composer with its This Mac / Run in cloud picker, and the channel list (now titled Channels) work as before.

• Needs you: the viewer's channels whose last run failed or is waiting on their answer (the same hints the sidebar uses from attention.ts; opening the channel clears them), then open PRs requesting the viewer's review.
• Pick back up: old Ace's ranking (pick-back-up.ts in githubnext/1111). A PR with a channel on it comes first, then the viewer's drafts, then their other open PRs, then issues assigned to them, newest first, up to 10. A fork's PR is skipped unless a channel is on it. Each row offers Continue, which opens the existing channel (a teammate's too, with their name shown), or Open in a channel, which uses the same prompt and create path as the Issues and PRs pages.
• Team pulse (deterministic): for each teammate, whether they're here or away (lobby presence), up to 3 active channels with summaries and a "working" mark, and channels where a run finished or failed since this browser last opened the project's dashboard. If there's no earlier visit, it covers the last day.

How channels are matched to PRs. A lane's branch is <channel prefix>/<lane>, and prefixes are unique on a host, so a PR's head branch names the channel that pushed it. When two hosts have the same prefix, the viewer's own channel wins. To support this, github-list PR items now include head and fork (headRefName, isCrossRepository). The new fields are optional, so older cached entries still load.

GitHub reads use the existing cached github-list requests with author:@me, review-requested:@me and assignee:@me searches, all through this host's gh account. A peer's account is never used.

Product calls

• PRs waiting on your review appear in Needs you, not in Pick back up. Their action is Continue when a channel exists, otherwise Open on GitHub, because the existing Open in a channel prompt is for continuing a PR, not reviewing one.
• Team pulse sits in the page's single column, not old Ace's right rail. The right sidebar slot belongs to channel details, and a single column works at phone width.
• "Since you were last here" is approximated by the last time this browser opened the project's dashboard. The timestamp is kept in localStorage, the same way attention state is.
• Issues aren't matched to channels, because nothing links a channel to the issue it was opened for. They always offer Open in a channel.

Remaining for #36

• Matching issues to the channel already on them (this needs feat(app): open GitHub items on GitHub or in a new channel #109/Start work from issues and PRs #28 to record the item).
• An optional model-written team pulse with a deterministic fallback, and the briefing.

Smoke test: an isolated host from source (temp ACE_HOME/ACE_CONFIG_HOME, ace serve --loopback) serving the built app, viewed in headless Chrome at desktop and phone widths, using a real clone of iamnbutler/toddler-game-center.

• Pick back up listed the viewer's 3 open PRs. PR Verify Ace with two machines on the tailnet #10 (branch mellow-delta/…) showed Continue for the mellow-delta channel, and clicking it opened that channel. The other two offered Open in a channel.
• A real Haiku run that used the question tool appeared in Needs you as "waiting for your answer".
• I checked the host's @me searches against repos that have review requests and assigned issues.

Not tested: Team pulse with real teammates (a loopback host has no peers or lobby), and clicking Open in a channel (its agent would push to a real PR).

Built in Ace

Built with Claude Code outside Ace, in a session already running there; no Ace gap involved.