docs(tests): finish the ephemeral-port wording (#570)

- docs/browser-testing-guide.md still described the shrink-only legacy list
  and the mobile suite's fixed ports; both are gone.
- CLAUDE.md: name the one fixed port left (codex-predictive-echo's separate
  lab server on 3222), keep "Never 3000", and say the guard refuses a fixed
  port rather than that it checks boundPort is read.
- The tui-client comment described the old "port + 1" dead port.

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

test/test-ports-guard.test.ts

@@ -9,8 +9,8 @@
  *
  * Two rules, both over every file under test/:
  * - A `WebServer` is built with the literal `0` as its port — `new WebServer(…)`, a
- *   class declared `extends WebServer`, or a destructured alias (`{ WebServer: T }`) —
- *   and the test reads `server.boundPort`.
+ *   class declared `extends WebServer`, or a destructured alias (`{ WebServer: T }`).
+ *   The test then reads `server.boundPort`, which this guard does not check.
  * - A raw server (`http`/`net`/Fastify `listen`, `new WebSocketServer`) never listens
  *   on a number or a `…PORT` constant: `listen(0, …)` / `{ port: 0 }`, then
  *   `address().port`.

test/tui/tui-client.test.ts

@@ -46,7 +46,7 @@ async function closedPort(): Promise<number> {
 }
 
 let port: number;
-/** Nothing listens one above the bound port: the "no server" path. */
+/** A port nothing listens on (`closedPort()`): the "no server" path. */
 let deadPort: number;
 let baseUrl: string;