Add Steeple Climb: the playable page and its place in the catalogue, on the rules in `steeple-climb/spire.js` #362

Make the Steeple Climb rules playable and listed, in the same shape as tide-crossing/ and bumper-cars/. Starts once #355 has landed steeple-climb/spire.js.

Done looks like:

• [ ] steeple-climb/index.html draws the seeded church steeple face with its holds and the weathercock at the top; tap a reachable hold (or pick it with the arrow keys and Enter) to test or trust it as the rules allow; U undoes where the rules allow and R restarts. The HUD shows height, moves and par. It drives the game only through the export of spire.js and adds no game rule of its own. The HUD reads from the rules state, and every move, refusal and end line is announced through an aria-live region.
• [ ] Follows the README Visual rules: 360x280 canvas via engine.js, fixed 30-degree camera, hard shadows screen-right, ambient motion held still under prefers-reduced-motion. A tested loose stone differs from a sound one by shape as well as colour (a crack drawn across it), and the reachable holds are outlined. 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 with id steeple-climb, title Steeple Climb, kind Climbing, input Tap, music: false and forged: true; the matching <li> in the root index.html; 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 steeple-climb that reaches an end line, serve.test.mjs asserts /steeple-climb/ and /steeple-climb/spire.js answer 200, a steeple-climb/page.test.mjs stays inside the per-game test budget the suite already holds to, playtest.test.mjs passes for the folder, and bun test passes. bun scripts/design-lint.ts passes.

Files: steeple-climb/index.html, steeple-climb/page.test.mjs, shell.js, index.html, README.md, rounds.mjs, serve.test.mjs, og/. Risk: shell.js, index.html, README.md and serve.test.mjs are shared with every other page pull; rebase before pushing. Fits: a builder.