Creates timeline_events plus the timeline_event_persons and
timeline_event_documents join tables, all FK columns ON DELETE CASCADE
(a person/document delete drops the join row, the event survives —
V71-class hardening). Two CHECK constraints push integrity to Postgres:
chk_timeline_event_range enforces event_date_end non-null IFF RANGE (a
strict biconditional, intentionally tighter than Document's open-ended
ranges), and chk_timeline_event_precision forbids exactly UNKNOWN while
keeping SEASON/APPROX legal. FK and query-column indexes added up-front
to avoid the V62 retrofit debt. Forward-only, additive DDL.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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