Add Bird Watch: the playable page and its place in the catalogue, on the rules in `bird-watch/watch.js` #181

A new game in the house style, mounted like the other forged games, built on the tested rules in bird-watch/watch.js.

Done looks like:

• [ ] bird-watch/index.html draws the garden, its perches and the birds as they land and fly off, and the bird named in each question, and drives it only through bird-watch/watch.js; it adds no game rule of its own. Tap the perch where the named bird sat, or pick it with the arrow keys and confirm with Space. Ambient motion only in leaves stirring. The HUD shows the round, answers right and binoculars left the rules report.
• [ ] Follows the README Visual rules: 360x280 canvas, fixed 30-degree camera, hard shadows screen-right, and ambient motion stopped under prefers-reduced-motion. Each species differs by silhouette as well as colour, so the game can be played without telling colours apart. The canvas aria-label says how to play. The rules popup is at most four lines. There is a #mute button and no .mp3 is committed.
• [ ] Listed in GAMES in shell.js as { id: 'bird-watch', title: 'Bird Watch', blurb: 'Remember where each bird perched', kind: 'Memory', input: 'Tap', accent: '#6b8f3a', music: false, forged: true }. It has the matching <li> in the root index.html, a building in the town from town.js like every other game, and appears in the README Games table and the list of games without music. bun scripts/og.mjs has been run.
• [ ] rounds.mjs has a scripted round for bird-watch that reaches the end line. serve.test.mjs asserts that /bird-watch/ and /bird-watch/watch.js answer 200. playtest.test.mjs passes for the folder, and bun test passes.

Files: bird-watch/index.html, shell.js, index.html, town.js if buildings are listed there, README.md, serve.test.mjs, rounds.mjs, og/. Risk: the appends conflict with other new-game pulls, so rebase on main before pushing. Fits: a builder.

Parked by the crew: the check stayed red through 2 automatic tries (pull #211 closed). Planner: split this smaller, or rewrite what done looks like; a person can also say what to try.

Parked by the crew: @vesper's run ended without a pull: the pull closed

Parked twice since a person last spoke here, so it is the planner's now. Every reason:

1. the check stayed red through 2 automatic tries (pull #211 closed)
2. @vesper's run ended without a pull: the pull closed

The planner splits it, replaces it with a fresh issue, or defers it; a person can also say what to try. Nothing starts here until then, and the board lists it.

Dropped by the planner: Bird Watch already landed on main in fa2d5a9 (pull #229). That commit adds bird-watch/index.html, its page test, the GAMES entry in shell.js, the root index.html item, the round in rounds.mjs and og/bird-watch.png. Nothing in this issue is left for the direction to need. No other issue waits for this one.