fix(review): rebuild Session Manager additions on the merged #146 implementation (PR #153)

- Hide the new btn-session-manager header button on phones: add it to the
  @media (max-width: 430px) display:none block in mobile.css (next to
  .btn-away-digest) and to KNOWN_PHONE_HIDDEN in the mobile-header policy
  test, closing the recurring phone-header-leak regression that was PR
  #153's red CI job.
- Put the session-manager header button on its own line in index.html
  (was crammed onto the away-digest line).
- app.js: drop session:updated from the unified-list SSE refresh trigger —
  it is batch-broadcast ~every 500ms per active session and would turn an
  open modal / visible welcome list into a sustained ~1 Hz full projects
  rescan loop; created/deleted (structural changes) are sufficient.
- terminal-ui.js _fetchUnifiedSessions: check the ApiResponse envelope and
  throw on failure so a 5xx surfaces via the caller's catch instead of
  rendering an empty history.
- terminal-ui.js _openSessionRowMenu: on re-entry, invoke the previous
  menu's close fn (stored as _openRowMenuClose) so its document/window
  listeners are detached rather than leaked; use claudeSessionId ||
  sessionId in the 'Resume session' menu item to match the main-row and
  Session Manager resume routing.

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

src/web/public/app.js

@@ -1426,8 +1426,11 @@ class CodemanApp {
     // visible welcome list) on session structural changes. Extra listeners on the
     // same EventSource — EventSource supports multiple listeners per event — so the
     // existing handlers above are untouched. Registered through addListener so they
-    // are torn down with the rest on reconnect.
-    for (const event of [SSE_EVENTS.SESSION_CREATED, SSE_EVENTS.SESSION_UPDATED, SSE_EVENTS.SESSION_DELETED]) {
+    // are torn down with the rest on reconnect. Only structural events (created /
+    // deleted) trigger a refetch: session:updated is batch-broadcast every ~500ms
+    // per active session, which would otherwise turn an open modal / visible welcome
+    // list into a sustained ~1 Hz full ~/.claude/projects rescan loop.
+    for (const event of [SSE_EVENTS.SESSION_CREATED, SSE_EVENTS.SESSION_DELETED]) {
       addListener(event, () => this._onSessionListMaybeChanged());
     }
   }