Extends the creating/updating hooks to capture the ambient actor
synchronously and freeze it onto every write:
- `__lastActor` on each record (whole-record attribution for Workbench badges)
- `__fieldActors` parallel to `__fieldTimestamps` (field-level attribution
for inline diff rendering — e.g. "AI changed due date, user changed title")
- `actor` on `_pendingChanges` rows so mana-sync + cross-device views can
distinguish AI- vs user-initiated writes
Also adds `kontextDoc` to v17 (missing from schema while module was live)
alongside the new `pendingProposals` table for staged AI intents.
Actor is captured in-hook rather than at emit time because
`trackPendingChange` is deferred via setTimeout and would otherwise lose
ambient context.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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