Schema v10 + view_ownership table. Cross-connector view name
collisions are detected and refused with an actionable ERROR rather
than silently last-write-wins. Pre-scan reconcile releases stale
ownerships in the same rebuild as a rename — but only when ALL
sources' pre-scans succeed (transient-IO defense; partial pre-scan
skips reconcile to avoid silently stealing a name).
26/26 view collision + orchestrator tests pass.
Refs #81 Group C.
