v2.3.3 — index lifecycle signal on /ws

Added

• Transient {type:'index'} message on /ws — started / completed /
  failed, carrying repo_path, project, branch, and best-effort stats
  (nodes, edges, frames, elapsed_ms; only elapsed_ms is guaranteed —
  a cache import knows no node/edge counts and a detached background index
  reports none at all). Emitted from the index_repository handler and from
  the child kickBackgroundIndex spawns, so a consumer learns an index
  finished instead of polling for it. Never persisted: no ULID, no events.db
  row, no backfill or catch-up participation, and it carries repo_path
  because index runs concern arbitrary checkouts while the socket binds one
  project. connectLiveSync gains an onIndex callback; older clients ignore
  the message through their existing default: branch.