fix(docker): require a per-session token on the VNC browser CDP bridge (#12571) (#13241)

Merged as part of the owner batch of 2026-09-11.

This PR had a live worktree in another session, so it sat outside the main 39. Merged on your explicit call, validated first rather than taken on trust: boarded with the other 10 worktree-held PRs into a consolidated worktree off `release/v3.8.51`.

- ESLint over every changed file: no errors
- `typecheck:core` clean; `check:dashboard-typecheck` OK; `check:changelog-integrity` OK
- complexity 2821 / baseline 3218 and cognitive-complexity 1272 / baseline 1437
- 203 of 208 assertions green. The 5 remaining (`guide-settings-route` ×4, `hard-session-lease-bypass-inventory` ×1) reproduce on the pure tip with nothing from this batch applied.
- `imageGeneration.ts` rebaselined 3259 → 3293 for #12945's image-only-model guard, landed separately in #13392 so nothing was pushed onto a live branch.

⚠️ base-red inherited: #12732 — provider count 356 vs 358 and `open-sse/utils/stream.ts` 3115 > frozen 3098, both reproducing on the pure tip.

.env.example

@@ -3021,6 +3021,7 @@ QUOTA_STORE_DRIVER=sqlite
 # OMNIROUTE_VNC_READY_MS=45000
 # OMNIROUTE_VNC_HARVEST_MS=20000
 # OMNIROUTE_VNC_CHROMIUM_ARGS=--remote-debugging-port=9222 --no-first-run --no-default-browser-check
+# OMNIROUTE_VNC_NETWORK=omniroute-vnc-browser-login
 
 # ─────────────────────────────────────────────────────────────────────────────
 # Data-dir alias (optional — open-sse/services/notionThreadSessions.ts)