test: replace product tests that fake the product with real-boundary tests (F)

- design: serve.test.ts drove an inline mirror server; now two tests run the
  real serve() on an ephemeral port (reload confinement, submit exit 0).
- setup-gbrain: rollback + voyage tests execute the template-extracted init
  blocks (3 sites) instead of drifted local bash copies.
- terminal-agent: internalHandler source greps replaced by a behavioral
  /internal/grant + /internal/revoke auth matrix (no/wrong/valid token).
- /health: server-security-surface and the server-auth / security-audit-r2 /
  sidebar-tabs source greps fold into one liveness-only check on the real
  body; the L4 sidecar wiring gets a behavioral /pty-inject-scan test.
- delete tautologies (browser-manager onDisconnect, memory-command #12),
  ios swiftui tap fixture self-check, memory-ingest put_page grep, detach
  source greps, sidebar-agent absence pins, dead-CSS pins + the dead CSS,
  security-audit-r2 Task 1 + the test-only meta-commands re-export,
  duplicate generated-SKILL.md checks.
- make-pdf coverage-gaps cases move into their owner test files.

docs/BROWSER_INTERNALS.md

@@ -162,5 +162,6 @@ file lost its only writer when sidebar-agent.ts was ripped, so the shield
 reported a permanent 'inactive' or a stale false-green 'protected' from
 leftover disk state. The live defenses (L1-L3 filters, L4 sidecar on the
 inject-scan path) report through their own call sites, never through
-/health. `browse/test/server-security-surface.test.ts` pins both the
-removal and the live L4 wiring. Do not re-document these as live.
+/health. `browse/test/extension-token.test.ts` pins the removal on the real
+/health body and `browse/test/pty-inject-scan.test.ts` pins the live L4
+wiring behaviorally. Do not re-document these as live.