Package Deltas: define the artifact and spell conflict tracer #308

This was generated by AI during triage.

Agent Brief

Category: enhancement
Summary: Define and test the Package Delta artifact using spell headers and effects.

Current behavior:
Packages have no data artifact. Base imports replace whole data families, and package-specific row changes have no durable claims or conflict checks.

Desired behavior:
Define a versioned canonical JSON Package Delta. It records Package identity, source hash, table, typed primary key, operation, and claimed fields. Unsigned 64-bit values use decimal strings with an explicit type. A partial update names only changed fields. An insert contains a complete row. Row deletion is not supported.

The tracer supports spell headers and child effects. It derives packed child keys from the claimed spell identifier, enforces the client-safe synthetic spell range, and rejects fixture-reserved identifiers. Two Packages may claim different fields on one row. Claiming the same field fails and names both Packages. Primary-key collisions on inserted rows also fail.

Key interfaces:

• Versioned Package Delta schema
• Pure parser, canonical serializer, and merger
• Spell and SpellEffect identifier policy
• Read-only check output

Acceptance criteria:

• Canonical serialization is byte-stable for equivalent input.
• Unknown versions, tables, fields, types, and malformed keys fail before any write.
• Same-row different-field claims merge.
• Same-field and inserted-key conflicts name both Packages and the exact claim.
• SpellEffect keys derive from the top-level spell identifier and effect index.
• The tracer accepts partial updates and complete inserts but refuses deletes.
• Tests cover fixture-reserved and non-client-safe spell identifiers.

Out of scope:

• Database application or import replay
• Tables outside spell headers and effects
• Datascript execution