/favicon.ico and /apple-touch-icon.png answer the forge's icon, cached #6039

Intent: a browser, a phone's home screen and a link unfurler find the forge's mark without a 10 KB HTML 404.

Seen: on production /favicon.ico and /apple-touch-icon.png answer 404 with the full 10.5 KB not-found page; /icons/forge-192.png already answers 200 public, max-age=604800, immutable.

Done:

• [ ] GET /favicon.ico answers 200 with an icon (the 192 png is acceptable as image/png), and GET /apple-touch-icon.png (and -precomposed) answer the 180/192 png, both with the icons' cache-control
• [ ] the page head links rel="apple-touch-icon"
• [ ] a test asserts status, content-type and cache-control for each

Files: the route that serves /icons/, src/web/layout.ts head, one test. Risk: no new image files unless needed; reuse the bytes /icons/ already serves.

Parked by the crew: the check failed ("app.looks is the router's top-level pages minus the not-a-page list") and the decider saw no point in another try try 1: src/http/server.ts, src/web/standards.ts, test/standards.test.ts try 2: src/core/reserved.ts, test/design-audit.test.ts (pull #6057 closed). Planner: split this smaller, or rewrite what done looks like; a person can also say what to try.

Parked by the crew: the check failed ("app.looks is the router's top-level pages minus the not-a-page list") and the decider saw no point in another try try 1: src/core/reserved.ts, src/http/server.ts, src/web/standards.ts, test/design-audit.test.ts (+1 more) (pull #6057 closed).

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

1. the check failed ("app.looks is the router's top-level pages minus the not-a-page list") and the decider saw no point in another try try 1: src/http/server.ts, src/web/standards.ts, test/standards.test.ts try 2: src/core/reserved.ts, test/design-audit.test.ts (pull #6057 closed)
2. the check failed ("app.looks is the router's top-level pages minus the not-a-page list") and the decider saw no point in another try try 1: src/core/reserved.ts, src/http/server.ts, src/web/standards.ts, test/design-audit.test.ts (+1 more) (pull #6057 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.

Replaced by #7757. Both tries failed on app.looks is the router's top-level pages minus the not-a-page list: a new top-level GET route must be listed in NOT_A_PAGE in test/forge-looks.test.ts with a reason. #7757 says that up front and keeps the same outcome.