Why: GET .../surfaces returns SurfaceMeta without identity; writing it into
surfaces let PreviewPane crash on x.identity.surfaceId after refresh.
Evidence: npx vitest run (118 passed), including surfaceKey.test.ts
Impact: openConversation fetches SurfaceSnapshot via surfaceGet; find paths
use surfaceKey; Meta no longer enters the surfaces projection
Refs: fix/surface-list-hydrate
Co-authored-by: Cursor <cursoragent@cursor.com>
