Starting a session from the welcome screen sets selectedProfileId and
then awaits the create POST. The profile watcher fires on the microtask
that the await yields, so the list refetch is issued while the POST is
still in flight — it returns a page that predates the new session, and
fetchSessions replaced the whole array, so the placeholder createSession
had just inserted was gone. The session only came back on a manual
refresh. Reproduced in a store test.

sessions.js now remembers a session it created along with the id of the
last list request that had already started at that moment, and a page
that started after the creation is still believed. So the rescue is
bounded by one round trip — it cannot turn into a ghost row: a request
that left once the session existed reports it missing and it goes, and
deleteSession clears the mark outright. Search and special-list pages
are never padded this way, since they answer a different question.

- sidebar: service-sessions toggle (special=true fetch replaces the
  regular list, active search drops out), muted style + robot icon on
  special items in the list
- settings: Synapse reactions panel — enable switch, completion push
  preference (always / only failures / never), notification destination
  (app / app+Synapse / Synapse, Synapse options disabled while no
  source key), reaction instructions editor with save + edit history
  (author and reason per version)
- stores: synapseReactions store; sessions store fetches respect
  showSpecial; getSessions passes special param
- vitest for api/session store/panel; dist rebuilt

- documentTitle: persistent nameById map — names for sessions beyond the
  loaded list page (list only holds ~30); map filled by fetches and
  loadSession meta, never wiped by later refetches
- createSession: placeholder inserted at the position the server list
  would give it (after pinned run, last_active desc) so refetch no
  longer visibly moves the new row
- SessionItem: skip empty .session-icons wrapper when no icons
- drawer breakpoint made exclusive (-sidebar-drawer 1280 -> 1279.98):
  viewport of exactly 1280px now gets the desktop sidebar

- fetchSessions merges into existing items (preserve object references)
  instead of wholesale array replacement — DynamicScroller reuses rows,
  the list no longer repaints/reflows on every refetch (measured: sidebar
  repaint spikes 8-17% per switch -> 0)
- AppSidebar.handleSelect no longer refetches the list on a plain select;
  refetch only when leaving search (the array still held search results)
- loadSession now lives only in handleSelect — SessionList.onSelect used
  to start a first load and handleSelect raced it with a second one
  (double fetch + double buildMessageList, incl. search-jump target)
- pinSession mutates in place instead of replacing every item object
- SessionItem.highlightText matches on the raw string so <mark> offsets
  stay correct when the text contains &/</>

Backend:
- GET /sessions now accepts `search` query param
- _session_summary computes match_indices and match_preview from messages
- pg_session_store: messages ILIKE added to search_list and count_all
- In-memory store: search_list also filters by message content

Frontend:
- AppSidebar: search toggle icon + debounced input, Ctrl+K shortcut
- SessionItem: highlight matching text, show match_preview from search
- SessionList: pass searchQuery to SessionItem
- SessionsStore: searchQuery/searchActive state, setSearch/clearSearch
- API layer: getSessions accepts search param
- MessageList: scroll to target message + brightness flash animation
- ChatStore: loadSession accepts targetMessageIndex, scrollToMessageIndex ref
- CSS: msg-flash keyframe animation in app.scss
- Tests updated for new getSessions signature

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

- Vitest + @vue/test-utils + happy-dom setup
- api/index.test.js: 8 tests for fetch wrapper, verbs, errors, FormData
- stores/chat.test.js: 23 tests for buildMessageList, WS handlers, load/clear
- stores/sessions.test.js: 6 tests for fetch, create, delete, pin, preview
- stores/profiles.test.js: 3 tests for fetch, auto-select, lookup
- composables/useWebSocket.test.js: 7 tests with MockWebSocket
- Export buildMessageList from chat store so tests can verify message parsing
- Update docs/testing.md with webclient stack, layout, and commands

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>