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

docs/adr/ADR-272-websocket-authentication-tickets.md

@@ -0,0 +1,169 @@
+# ADR-272: WebSocket authentication tickets
+
+- **Status**: accepted
+- **Date**: 2026-07-22
+- **Deciders**: RuView maintainers
+- **Tags**: auth, websocket, security, sensing-server
+- **Related**: ADR-271 (Cognitum OAuth resource server), ADR-055 (integrated sensing server), PR #1313 (the exemption this supersedes), cognitum-one/dashboard ADR-060
+
+## Context
+
+`bearer_auth` gates `/api/v1/*`. WebSocket upgrade endpoints were exempt, for a
+real reason: a browser's `WebSocket` constructor cannot attach an
+`Authorization` header to the handshake, so a gated socket is simply
+unreachable from page JavaScript. `/ws/sensing` and `/ws/introspection` sat
+outside `PROTECTED_PREFIX` entirely; `/api/v1/stream/pose` was added to an
+explicit `EXEMPT_PATHS` list by PR #1313.
+
+The reasoning was sound. The consequence was not, and it was measured rather
+than argued. On a server with `RUVIEW_API_TOKEN` set — an operator who believes
+authentication is ON — a real WebSocket handshake carrying **no credential at
+all**:
+
+```
+/ws/sensing            -> 101 Switching Protocols
+/ws/introspection      -> 101 Switching Protocols
+/api/v1/stream/pose    -> 101 Switching Protocols
+/api/v1/models         -> 401 Unauthorized        (control)
+```
+
+**The control plane was locked and the data plane was open.** `/ws/sensing`
+carries the live sensing output — presence, pose, breathing and heart rate.
+`/ws/introspection` exposes internal pipeline state. For the ADR-055 desktop
+topology (server bundled in the app, loopback only) that is bounded. For the
+LAN/hub deployment RuView also supports, anyone who can reach the port can
+watch the sensor.
+
+ADR-271 sharpened the contrast rather than causing it: the REST surface is now
+genuinely strong — offline-verified Cognitum tokens, scope-separated
+destructive routes — which makes an ungated data plane the obvious way in.
+
+*Precision about the evidence:* the handshake completing was verified. A
+payload frame was not captured in that window, so the finding is "the
+connection is established without a credential", not "data was read".
+
+## Decision
+
+Gate every WebSocket upgrade. Accept **either** of two credentials, chosen to
+match what each kind of client can actually do.
+
+### 1. Native clients send a bearer on the upgrade
+
+The Python client, the Rust CLI and the TypeScript MCP client are not browsers
+and have never been subject to the header limitation. They send a normal
+`Authorization: Bearer` on the handshake. Routing them through a ticket would
+add a round-trip and a second credential path for no benefit.
+
+### 2. Browsers exchange their credential for a single-use ticket
+
+`POST /api/v1/ws-ticket` is an ordinary authenticated request — where headers
+*do* work — and returns an opaque ticket the page appends as
+`?ticket=<value>` on the socket URL.
+
+**A credential in a URL is normally a mistake.** URLs reach access logs,
+`Referer` headers and browser history. Three properties bound this one, and all
+three are load-bearing:
+
+| Property | Why it matters |
+|---|---|
+| **Single use** — consumed on the first upgrade attempt, valid or not | A ticket found in a log is already spent |
+| **~30 second TTL** | Long enough to open a socket; not long enough to harvest |
+| **Not the credential** — authorizes one WebSocket | Cannot be replayed against `/api/v1/*`, cannot be refreshed, carries no reusable identity |
+
+The long-lived bearer token is still never placed in a URL.
+
+A ticket **inherits the issuing principal's scopes**, so a `sensing:read`
+session cannot mint one that outranks itself, and a ticket from a token without
+`sensing:read` is refused at the upgrade.
+
+### 3. WebSocket paths are matched by **prefix**, not by an allowlist
+
+Anything under `/ws/` is treated as an upgrade path, plus the one endpoint that
+lives outside it (`/api/v1/stream/pose`).
+
+This is the most important detail in the ADR. An allowlist means every
+WebSocket route added later is ungated until someone remembers to extend it —
+the same bug, reintroduced on a delay. It is 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 under
+an allowlist. Prefix matching gates it on arrival.
+
+New WebSocket routes should live under `/ws/` and inherit gating for free.
+
+### 4. A migration escape hatch, deliberately uncomfortable
+
+`RUVIEW_WS_LEGACY_UNAUTHENTICATED=1` restores the previous behaviour. Gating
+these paths **breaks a browser UI that has not yet been updated to fetch a
+ticket**, and not every deployment can update server and UI in lockstep.
+
+It is a migration aid, not a supported configuration:
+
+- It logs a warning on every boot naming the actual exposure — "the live
+  sensing stream — presence, pose and vital signs — is readable by anyone who
+  can reach this port" — rather than something an operator can skim past.
+- Its blast radius is exactly the WebSocket paths. A test pins that it does not
+  weaken `/api/v1/*`.
+- It is read **once at construction**, so changing the environment cannot
+  silently open the paths on a running server.
+
+The alternative — a clean break with no hatch — was considered and rejected as
+sequencing, not principle: a hard break tempts an operator into turning auth off
+entirely, which is strictly worse than a narrow, loudly-announced exception.
+The hatch should be removed once the shipped UI fetches tickets.
+
+### 5. Deployments with auth off are unchanged
+
+No credential configured ⇒ the middleware is the same no-op it has always been.
+Pinned by a test.
+
+## Consequences
+
+- The measured hole is closed: all three paths now return `401` to a
+  credential-less handshake, while a bearer or a valid ticket returns `101`.
+- Browser UIs need updating. Shipped in the same change for
+  `sensing.service.js`, `websocket-client.js` and `observatory/js/main.js` via
+  a shared `withWsTicket()` helper; a ticket is minted per connection attempt
+  and never cached, because it is single-use and short-lived.
+- A UI running against a server that predates this ADR still works: the helper
+  treats `404` from `/api/v1/ws-ticket` as "no ticket needed".
+- One more round-trip before a browser opens a socket. Negligible against a
+  stream that then runs for minutes.
+- Tickets live in memory, capped at 512 outstanding and self-healing as they
+  expire, so an authenticated but misbehaving caller cannot grow the store
+  without bound. In-memory is correct rather than convenient: a ticket
+  surviving a restart would outlive the server that vouched for it.
+
+## Supersedes
+
+PR #1313's `enabled_exempts_pose_stream_websocket`, which asserted the
+exemption. Its premise about browsers was correct and is preserved here; its
+conclusion is replaced. The test was renamed and inverted rather than deleted,
+with the history in its doc comment, and the half that still matters — the
+WebSocket rule must not leak to other `/api/v1/*` paths — is kept.
+
+## Deliberately not done
+
+- **`/health*` stays ungated.** Orchestrator probes hit it anonymously, and
+  that is the point of a liveness endpoint. `/health/metrics` is included in
+  that exemption; if metrics ever carry occupancy-derived values this should be
+  revisited, because that would make them sensing data wearing an ops label.
+- **`/ui/*` stays ungated.** It is static assets; the data behind them is
+  gated.
+- **No revocation of an issued ticket.** It expires in seconds and is
+  single-use; a revocation path would be more machinery than the exposure
+  justifies.
+- **No ticket for native clients.** They can send a header, so they should.
+
+## Implementation
+
+`v2/crates/wifi-densepose-sensing-server/src/ws_ticket.rs` (store),
+`src/bearer_auth.rs` (gating), `src/main.rs` (`POST /api/v1/ws-ticket`),
+`ui/services/ws-ticket.js` plus the three call sites.
+
+Tests: 12 store, 9 gating, 4 path-matching. Store coverage includes single-use
+enforcement, replay refusal, expiry refusal *and* pruning, 256-bit
+unpredictability, cap enforcement and self-healing, and `?myticket=x` not being
+read as `?ticket=x`. Gating coverage includes every known WS path refusing an
+unauthenticated upgrade, bearer acceptance, ticket single-use, a ticket being
+useless against REST, the escape hatch working *and* not weakening REST, and
+auth-off behaviour unchanged.