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/services/sensing.service.js

@@ -1,3 +1,4 @@
+import { withWsTicket } from './ws-ticket.js';
 /**
  * Sensing WebSocket Service
  *
@@ -65,7 +66,7 @@ class SensingService {
 
   /** Start the service (connect or simulate). */
   start() {
-    this._connect();
+    void this._connect();
   }
 
   /** Stop the service entirely. */
@@ -120,13 +121,26 @@ class SensingService {
 
   // ---- Connection --------------------------------------------------------
 
-  _connect() {
+  // async because the server gates `/ws/sensing` (ADR-272) and a browser
+  // cannot set an Authorization header on an upgrade — so we mint a
+  // single-use ticket first. Minted per connect attempt, never cached: a
+  // ticket is valid once and expires in seconds, so reusing one across
+  // reconnects would fail on the second attempt.
+  async _connect() {
     if (this._ws && this._ws.readyState <= WebSocket.OPEN) return;
 
     this._setState('connecting');
 
+    let url = SENSING_WS_URL;
     try {
-      this._ws = new WebSocket(SENSING_WS_URL);
+      url = await withWsTicket(SENSING_WS_URL);
+    } catch {
+      // Ticket minting is best-effort: against a server with auth off, or one
+      // predating ADR-272, connecting without a ticket is correct.
+    }
+
+    try {
+      this._ws = new WebSocket(url);
     } catch (err) {
       console.warn('[Sensing] WebSocket constructor failed:', err.message);
       this._fallbackToSimulation();
@@ -184,7 +198,7 @@ class SensingService {
 
     this._reconnectTimer = setTimeout(() => {
       this._reconnectTimer = null;
-      this._connect();
+      void this._connect();
     }, delay);
 
     // Only start simulation after several failed attempts so a brief hiccup