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.

docs/reference/ENVIRONMENT.md

@@ -1452,6 +1452,7 @@ Containerized Chromium+VNC used for interactive browser-login credential capture
 | `OMNIROUTE_VNC_READY_MS` | `45000` | `src/lib/vncSession/manifest.ts` | Timeout (ms) waiting for the containerized browser to become CDP-ready. |
 | `OMNIROUTE_VNC_HARVEST_MS` | `20000` | `src/lib/vncSession/manifest.ts` | Timeout (ms) for harvesting the captured session/cookies after login completes. |
 | `OMNIROUTE_VNC_CHROMIUM_ARGS` | `--remote-debugging-port=9222 --no-first-run --no-default-browser-check` | `src/lib/vncSession/manifest.ts` | Extra command-line flags passed to the containerized Chromium. |
+| `OMNIROUTE_VNC_NETWORK` | `omniroute-vnc-browser-login` | `src/lib/vncSession/manifest.ts` | Dedicated Docker network the VNC login container joins (#12571) instead of the default bridge, so sibling containers can't reach its CDP bridge port. |
 | `VIBEPROXY_DATA_DIR` | _(unset)_ | `open-sse/services/notionThreadSessions.ts` | **Legacy alias** for `DATA_DIR`, checked only after both `DATA_DIR` and `OMNIROUTE_DATA_DIR` are unset. Locates the Notion web-thread session cache (`<dir>/notion-web-thread-sessions.json`). |
 
 ---
@@ -1590,6 +1591,7 @@ Used by `src/lib/vncSession/manifest.ts` to configure Docker-based headless Chro
 | `OMNIROUTE_VNC_MAX_SESSIONS`          | `4`                           | `src/lib/vncSession/manifest.ts`  | Maximum concurrent VNC sessions.                                               |
 | `OMNIROUTE_VNC_READY_MS`              | `45000`                       | `src/lib/vncSession/manifest.ts`  | Browser readiness timeout (ms).                                                |
 | `OMNIROUTE_VNC_HARVEST_MS`            | `20000`                       | `src/lib/vncSession/manifest.ts`  | Harvest/cleanup timeout (ms).                                                  |
+| `OMNIROUTE_VNC_NETWORK`               | `omniroute-vnc-browser-login` | `src/lib/vncSession/manifest.ts`  | Dedicated Docker network the container joins (#12571), off the default bridge. |
 | `VIBEPROXY_DATA_DIR`                  | _(unset)_                     | `open-sse/services/notionThreadSessions.ts` | Directory for Notion thread session persistence.                               |
 
 ### Internal service auth