test(guard): no legacy list left; flag raw listeners on a fixed port (#440)

With the sweep done, LEGACY_FIXED_PORT_FILES and its staleness test go. A second rule flags a raw listen(<number or …PORT>) and a port: with a number or …PORT constant inside listen({ … }) or new WebSocketServer({ … }); a socket path and a lower-case variable pass. CLAUDE.md, AGENTS.md, CONTRIBUTING.md and the wiki's Contributing page lose the mobile exception, and CLAUDE.md names closedPort() instead of port + 1.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/wiki/Contributing.md

@@ -63,9 +63,8 @@ provide what they need; that means "not runnable here", not a regression.
 Tests are tmux-safe by design: under vitest the tmux layer becomes an in-memory mock, so
 tests cannot touch real sessions. If you add a test that binds a port, bind port 0
 (`new WebServer(0, …)` + `server.boundPort`, or `listen({ port: 0 })` + `address().port`),
-or use `app.inject()` when no socket is needed. Never 3000. Mobile tests (`test/mobile/**`,
-via `createTestServer(PORT)`) keep the fixed ports in `test/mobile/README.md` for now,
-because that helper caches servers by port.
+or use `app.inject()` when no socket is needed. Mobile tests call `createTestServer()` and
+read `server.boundPort`. Never 3000.
 
 ## Finding your way around