music-history-db: Specify stable identity, merge, and redirect semantics

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Finding

The specification requires internal stable identifiers and deduplication but does not define identifier generation, alias handling, entity merges, tombstones, redirects, or concurrent pull-request conflict behavior. These omissions risk broken references and non-deterministic reconciliation.

Relevant sections: entities, events and assertions, testing strategy, and refresh workflow in tools/specs/music-history-db/KSER_Music_History_Technical_Implementation_Strategy.md.

Required decision

Define deterministic identity and lifecycle rules for entities, events, assertions, places, and relationships.

Acceptance criteria

• Define stable-ID generation and immutability rules.
• Define the role of external authority IDs without making them the internal primary key.
• Define aliases, merges, splits, redirects, and tombstones.
• Preserve referential integrity and merge history.
• Define deterministic reconciliation and concurrent-PR conflict handling.
• Add tests for duplicate discovery, merge, split, and upstream identifier changes.