Beta15.7 semantic correctness candidate

[brik64-admin]

Summary

Prepares BRIK64 CLI v0.1.0-beta.15.7 as a semantic-correctness release candidate.

Implemented:

• strict certify/type checks for numeric coercion and return type mismatches
• return exhaustiveness validation
• reserved identifier validation
• required PCD file header and migrate --write repair path
• deterministic integer division helpers for TS/Python to match Rust semantics
• lift precision blocking for f64 literals inferred into i64 candidate PCDs
• Beta15.7 gates, package build, package smoke, and evidence

Evidence

PASS:

• npm run gate:beta15.7:semantic-correctness
• npm run gate:beta15.7:pre-public-rc
• npm run package:beta15.7:local
• npm run smoke:beta15.7:package

Blocked:

• npm run attempt:beta15.7:l6-generation

L6 blocker: remote materializer is still hardcoded to Beta15.6 and rejects Beta15.7 with version_mismatch. See docs/operations/BETA15_7_L6_MATERIALIZER_BLOCKER.md and evidence/beta15_7-l6-generation/gate-report.json.

Release Status

Do not merge as public release and do not publish Beta15.7 until the L6+N5 lane generates/installs a Beta15.7 materializer capability and the L6 generation gate passes with fresh evidence.