Handoff + migration spec incorrectly claimed Phase 9 added a new
parent_pilot_session_id FK. The implementation reuses the existing
ai_session_id column; the migration only adds the origin discriminator
+ partial unique index. Also: ScriptBuilderTab wraps ScriptBuilderChat
and ScriptBodyEditor (Monaco), not "ScriptBuilderChat in ephemeral
mode" — there is no ephemeral mode on the presentational component.
Applies applied_at call-site specifics: handleScriptDecision stamps
on one_off/draft_template, TemplateMatchPanel stamps on onMarkRun,
Script Builder tab Submit does not stamp.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>