- Serialize push/coalesce: replace ad-hoc scheduled/running/rerun booleans
  on _pushTabs/_pushSessions with a deferred (_*Next + _*ResolveNext)
  pattern, so callers can await emissions for ordering.
- Reorder _pushSessions body to emit before _reconcile so the UI doesn't
  wait for a slow BrowserTracker.create.
- Latest-wins coalesce for _switchAttachedTo via _pendingSwitchPage and a
  shared in-flight promise; replaces the .catch().then() chain trick.
- _handleAttachedPageClose: skip fallback attach when the context is
  already closed.
- closeSession reuses the cached browser tracker when present.
- Wrap page.title() and faviconUrl() in a withTimeout helper.
- Async onclose: clean up the recording dir and close+unlink stream files.

- Replace anyConnection() helper with a hasConnection ManualPromise
  that callers await before fanning out to all current connections.
- triggerAnnotate(signal) now returns the AnnotationResult (or undefined
  when aborted) via a ManualPromise; the caller writes the result to its
  socket. Removes the waitingSockets bookkeeping from the server core.
- Wrap the per-message socket handler in a single try/catch/finally;
  errors are serialized as {error} so the annotate client surfaces them.
- Collapse the createWebSocket connection setup to a single const.

Make _handleAttachedPageClose async and await _switchAttachedTo before
_pushTabs, so a single broadcast reflects the new attached page instead
of pushing twice with a wrong intermediate state.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

When switching the attached page, the server emitted the first frame
of the new page before the page-change tabs event. The client clears
liveFrame on page change, so the dropped frame left CLI annotate
stuck in cliAnnotatePending forever (static pages emit no further
frames).

Serialize tabs emit before screencast start so the wire ordering is
always tabs then frame.

Replace _pushTabs/_runPushTabs (which re-fetched title+favicon for every
page on every event) with:
- _tabDetails cache keyed by Page
- sync _emitTabs() that builds tabs from the cache and prunes orphans
- async _updateDetails(page) that refreshes one page and re-emits

BrowserTracker now fires per-page events (onPageNavigated, onPageClosed)
plus onContextClosed, so only the affected page is re-fetched. Drops the
redundant framenavigated listener in AttachedPage.init.

Tab.title becomes optional in the channel (sidebar already tolerates it).