Add verification-status model to schema

[TommiLindfors]

Scope

Add a verification_status field model to the schema, implementing the verification ladder: discovered -> structured-from-source -> source-checked -> expert-reviewed -> published -> stale-review -> superseded. Define allowed transitions and ensure all publishable objects include this field.

Source links

• Internal: Clarvia verification ladder specification
• Existing seed data convention in data/

Acceptance criteria

• verification_status enum defined in schemas
• Allowed values match the verification ladder
• All publishable object schemas require this field
• Existing seed data updated to include the field
• Validation passes
• Review status assigned

Trust level

maintainer-only

[TommiLindfors]

Closing as completed. Verification status model is implemented across all schemas with enum values: discovered, structured-from-source, source-checked, expert-reviewed, published, stale-review, superseded.