fix(review): WS state machine, per-tab supersede key, backoff, dot CSS (PR #149)

- _wsState now transitions through the full lifecycle: _connectWs() sets
  'connecting', ws.onopen (inside the this._ws === ws guard) sets 'connected',
  _disconnectWs() resets to 'disconnected' — the connection chip's "WS" state
  was previously unreachable (stuck on "WS…"/"HTTP" forever).
- WS registry supersede is now keyed per TAB: the upgrade URL sends
  cid = clientId + ':' + per-page nonce (reusing the constructor's page UUID),
  while input frames keep the bare browser clientId for seq dedup — two
  tabs/windows on one session coexist instead of 4010-evicting each other in a
  perpetual 5s ping-pong; a genuine same-tab reconnect still supersedes.
- Exponential backoff engages: _disconnectWs() no longer zeroes
  _wsReconnectAttempts (it's called at the top of _connectWs, so every retry
  replanned at attempt 0 → ~0ms tight reconnect loop during outages); onopen
  resets the counter on success.
- styles.css: add .connection-dot.connected (green) and .connection-dot.fallback
  (yellow) — both states rendered an invisible dot (no rule existed).
- Remove smuggled dead code: resolveMonitorRowLabels/CodemanMonitorLabels
  (COD-122, no consumer, referenced test doesn't exist) and the never-written
  _wsLastClose/_wsInputSendCount/_httpFallbackSendCount diagnostics.
- Tests: new test/ws-state-lifecycle.test.ts drives the REAL
  _connectWs/onopen/onclose/timer cycle (state transitions, escalating backoff
  delays, composite cid on the upgrade URL); registry two-tab coexistence test;
  static check that every emitted connection-dot class has a styles.css rule.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

test/ws-reconnect-plan.test.ts

@@ -6,8 +6,7 @@
  * number of consecutive reconnects already attempted, it returns the action to
  * take (`reconnect` | `retry-fallback` | `give-up`) and a backoff delay. It is
  * exposed on `window.CodemanWsReconnect` and tested here in a plain node VM
- * context (no jsdom — jsdom env setup is broken on some hosts), mirroring the
- * `CodemanMonitorLabels` harness in test/monitor-row-labels.test.ts.
+ * context (no jsdom — jsdom env setup is broken on some hosts).
  */
 import { readFileSync } from 'node:fs';
 import { resolve } from 'node:path';