Chat layout: roster, channel feed, composer

- The flock is a member list with live status (perched, flying,
  waiting on you, grounded); a scrolling strip on phones
- The Sentry and crows post into one channel; approvals are inline
  buttons on their messages; verdicts show as reactions
- "Who's flying" line above the composer; Ctrl/Cmd+Enter to send
- Consecutive messages from one author group under one name
- RIVE_CONTRACT.md: roster size and still message avatars

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UQnSw4RRWp8uqpj3nsnnXF

RIVE_CONTRACT.md

@@ -2,7 +2,7 @@
 
 The animator builds `crows.riv` against this file, and the web code drives it from the events in `EVENTS.md`. Both sides build against this file, so change it first and then the code. Each animation exists only because an `EVENTS.md` event fires it.
 
-Style: Duolingo-like behavior, pen-and-ink look: cream paper, ink linework, stipple shading (see `ui/src/style.css`). Smokey's crow art (`art/crow.svg`) is the character; keep its silhouette. Expressive crows that react through motion (hops, tilts, spins) and never change size, with readable silhouettes at 96 pixels. Sparkles mean celebration only. The approve and reject buttons stay in HTML for v1 (see "Why buttons stay in HTML").
+Style: Duolingo-like behavior, pen-and-ink look: cream paper, ink linework, stipple shading (see `ui/src/style.css`). Smokey's crow art (`art/crow.svg`) is the character; keep its silhouette. Expressive crows that react through motion (hops, tilts, spins) and never change size, with readable silhouettes at 40 pixels (the chat roster size). Sparkles mean celebration only. The approve and reject buttons stay in HTML for v1 (see "Why buttons stay in HTML").
 
 ## Rive approach: data binding, not inputs
 
@@ -21,7 +21,7 @@ Rive now marks state machine inputs as deprecated and recommends data binding fo
 | `Perch` | later | A scene with a branch of crows rendered as an Artboard List of `Crow` items ([lists](https://rive.app/docs/editor/data-binding/lists.md)), plus flock-wide celebrations. |
 | `Splat` | later | A full-screen "gift on your windshield" overlay for the prank. |
 
-In v1, the web page puts one `Crow` canvas per visible crow and lays them out with HTML and CSS. The Sentry and Elder are **variants** of `Crow`, not separate artboards, so the whole cast shares one rig.
+In v1, the web page is a chat room: one animated `Crow` canvas per crow in the member roster (sidebar on desktop, a scrolling strip on phones), about 40 pixels. Message avatars are still images, not Rive. The Sentry and Elder are **variants** of `Crow`, not separate artboards, so the whole cast shares one rig.
 
 Artboard spec: 256 × 256, transparent background, crow centered with its feet on a baseline 40 pixels from the bottom, so the crows line up in a row.