Why: U4 read-only experience - surface.updated events project into a
surfaces slice with a strict revision guard (stale/duplicate events
never overwrite; server snapshot is the single owner), preview tabs
gain a surface: kind that renders SurfaceView (doc-refs bridge into
artifact previews), a new page auto-opens a tab without stealing the
user's active non-surface tab, and opening a conversation reloads the
authoritative surface list so refresh/断线 restores pages.
Evidence: tsc clean; vitest 87/87 including new surface projection
tests (stale/duplicate/multi-surface); UI SurfaceView suite green in
its repo.
Impact: Frontend-only; no backend or contract changes.
Refs: Core PRs #27/#28; UI PRs #42/#43/#44; Dev task
feature/generative-ui-u4
weichen