Deterministic Core primitives

[knqiufan]

Canonical primitives for the sqlite-fts profile. May start in parallel with the M1 Client.

Scope

• JCS, NFC, hash, Source/Artifact/Trigger refs, UTF-8 byte budgets
• Fake-store state traces before persistence writes
• Byte-for-byte agreement with the Python rfc8785 oracle

Done when

• Python and TypeScript produce the same canonical bytes on the shared fixtures
• Illegal Unicode and integer boundaries fail the same way

See docs/roadmap.md, ADR 0001, and ADR 0006.