feat(ui): fetch WebSocket tickets, prefix-match WS paths, and write ADR-272

Completes ADR-272. Three parts.

1. PREFIX MATCHING, not an allowlist. Anything under `/ws/` is a WebSocket path,
   plus `/api/v1/stream/pose` which lives outside it. An allowlist means every
   WebSocket route added later ships ungated until someone remembers to extend
   it — the same bug reintroduced on a delay. Not hypothetical:
   `/ws/train/progress` (ADR-186, arriving with PR #1387) is ALREADY referenced
   by ui/services/training.service.js and would have shipped unauthenticated.
   Pinned by a test that asserts it is gated before it exists.

2. UI wiring. A shared `withWsTicket()` helper mints a ticket immediately before
   each connection attempt — never cached, because a ticket is single-use and
   expires in seconds, so reusing one across reconnects fails on the second
   attempt. Wired into the three sites that open gated sockets:
   sensing.service.js, websocket-client.js, observatory/js/main.js.

   It degrades in both directions on purpose: no stored token means auth is off
   and no ticket is needed; a 404 from /api/v1/ws-ticket means a server
   predating this ADR, which still exempts WebSockets, so connecting without a
   ticket is correct there. The same UI therefore works against old and new
   servers, which is what makes the escape hatch removable later rather than
   permanent.

   The long-lived bearer token is still never put in a URL — only the ticket is.

3. ADR-272 itself. Previously cited in five places without existing; the same
   dangling-reference mistake made with ADR-271 earlier today, so it is written
   before this lands rather than after someone notices.

   It records the measured before/after, why a credential in a URL is
   acceptable here specifically (single use, seconds-long, not the credential),
   why the escape hatch exists and why it is deliberately uncomfortable, and
   what is deliberately NOT done — including that /health/metrics stays ungated,
   with the caveat that this should be revisited if metrics ever carry
   occupancy-derived values, since that would make them sensing data wearing an
   ops label.

Tests: 526 sensing-server (4 new path-matching), 82 ruview-auth. JS
syntax-checked with `node --check`; there is no UI test suite to extend.

Co-Authored-By: Ruflo & AQE

ui/observatory/js/main.js

@@ -8,6 +8,7 @@
  * - Dot-matrix mist body mass, particle trails, WiFi waves, signal field
  * - Reflective floor, settings dialog, and practical data HUD
  */
+import { withWsTicket } from '../../services/ws-ticket.js';
 import * as THREE from 'three';
 import { OrbitControls } from 'three/addons/controls/OrbitControls.js';
 
@@ -462,7 +463,7 @@ class Observatory {
             console.log('[Observatory] Sensing server detected at', base, '→', wsUrl);
             this.settings.dataSource = 'ws';
             this.settings.wsUrl = wsUrl;
-            this._connectWS(wsUrl);
+            void this._connectWS(wsUrl);
           } else {
             tryNext(i + 1);
           }
@@ -472,10 +473,13 @@ class Observatory {
     tryNext(0);
   }
 
-  _connectWS(url) {
+  // async: `/ws/sensing` is gated (ADR-272); mint a single-use ticket first.
+  async _connectWS(url) {
     this._disconnectWS();
+    let wsUrl = url;
+    try { wsUrl = await withWsTicket(url); } catch { /* auth off or pre-ADR-272 server */ }
     try {
-      this._ws = new WebSocket(url);
+      this._ws = new WebSocket(wsUrl);
       this._ws.onopen = () => {
         console.log('[Observatory] WebSocket connected');
         this._hud.updateSourceBadge('ws', this._ws);