Get Claim By Id

Canonical single-claim fetch.

Visible to:

• claimant on this claim (uid = claimant_id)
• activity owner / org admin / platform admin (_assert_can_manage_claims gate)

Returns the full claim row with all drawer fields:

• id, activity_id, claimant_id, organization_id
• status, message, proposed_changes
• owner_review_deadline, extensions_used, dispute_reason, escalated_at
• reminders_sent, created_at, resolved_at
• draft_claimant_* fields (anon-draft contact info)
• claim_method, claimant_relationship_label, imported_source_acknowledged
• activity_title, creator_id, claimed_by
• first_name, last_name, display_handle, verification_status
• organization_name
• viewer_role: 'claimant' | 'owner_or_admin'

Terminal claims (approved_*, rejected, revoked, superseded) are returned; notifications for resolved claims must remain openable.

403 if neither claimant nor owner. 404 if claim not found.