pakka v0.19.0

Policy floor: a committed .pakka/policy.json is enforced in the binaries — confidence-threshold clamps apply only in the strict direction, locked guard categories ignore learned overrides and fail closed on unknown names, input-file compression can be locked off against any local opt-in, and a present policy forces the commit gate on regardless of local autoGate. Malformed or newer-versioned policy fails closed; absent policy preserves prior behavior exactly, with a per-run policy-state audit note so fail-open is observable. Distribution is git itself — no server, no dial-home. DX: review-pass markers are now diff-bound for freshness — a marker matching the staged diff stays valid 30 minutes instead of expiring on a 5-minute wall clock (1-hour hard ceiling; policy may lower). Assets CI-built with SLSA provenance attestation, SHA256SUMS, CycloneDX SBOMs.