Limitcast 0.19.2

Fixes two repository optimizer correctness issues:

• Learned command replacements now preserve the verification check, including when reading previously saved facts.
• Maps generated from dirty working trees no longer contaminate the cache reused after restoring clean source; legacy caches regenerate once.

This patch also supplies the LimitCast icon in Codex plugin settings and pins every plugin command to 0.19.2.

Validation: 258 tests, lint, privacy checks, and an isolated packaged-CLI regression smoke test passed. No real-world token-savings claim is made.