Sprint 227 Plan: Rust Harness Stability + Cross-Catalog Closure

Goal

Remove residual Rust harness-induced test failures and re-validate parity closure on both hard catalogs.

Step 2174: Patch rust gate harness to default-initialize PriorityQueue safely.
Step 2175: Re-run focused hard subset with strict parity mode.
Step 2176: Re-run fullstack/multifile hard set with strict parity mode.
Step 2177: Require both metrics to be zero:
- ab_prod_divergence_count
- ab_consistency_blocked_count
Step 2178: Publish dated execution tracker and registry updates.