/rooms: add left-nav link + a lobby/index (rooms list with needs-you + last-activity)

## Gap (operator, 2026-07-02) #39 shipped the per-project operator feed at `/rooms/{project:slug}`, but there's (a) NO left-nav link to it, and (b) no index/lobby — nowhere to land if you don't already have a project slug in the URL. ## Build 1. **Left-nav link** for the operator feed/rooms — match the existing nav pattern (e.g. the Briefs subitems #47/#59 added). Top-level "Rooms" (or under an activity section) is fine. 2. **/rooms lobby (index):** a Livewire index listing the per-project rooms (projects that have daemons/activity), each linking to its `/rooms/{project}` feed. For each room show at-a-glance signal: **needs_you count + last-activity time** (reuse #39's FeedService classification), sorted needs_you-first / most-recent, so the operator sees which room needs attention. 3. Optional: a combined "all projects" feed view — but the lobby list is the minimum. ## Acceptance - Left-nav link to rooms present; `/rooms` lobby lists rooms with needs_you count + last-activity, each linking to its per-project feed. Livewire/feature tests. No migration. sqlite tests only; pint; match the bloom design system. No Horizon reload. `Brief:` trailer with this id. ## Provenance Operator 2026-07-02: "no nav link for /rooms + no index/lobby — do something about that." Builds directly on #39 (the /rooms feed + FeedService).