Problem
Cascade defines `actor` (extends PersonEntry), `cascade_org` (extends OrganizationEntry), and multiple event types (extends EventEntry). After journalism-investigation plugin exists, these should extend the richer journalism-investigation types to inherit financial tracking, source management, and evidence chain capabilities.
Scope
Change `ActorEntry` to extend journalism-investigation's person type (or keep extending PersonEntry if journalism-investigation reuses core)
Change `CascadeOrgEntry` to extend journalism-investigation's organization type
Change `CascadeEventEntry`, `TimelineEventEntry`, `SolidarityEventEntry` to extend `InvestigationEventEntry`
Add journalism-investigation as a dependency in Cascade's `pyproject.toml`
Ensure all Cascade-specific fields are preserved
Verify all 10 existing Cascade entry types still load/save correctlyAcceptance Criteria
All existing Cascade tests pass
Cascade types inherit journalism-investigation fields (sources, verification_status, etc.)
No frontmatter changes required in existing KB files (backward compatible)
Plugin load order handles the dependency correctly