chore(ai-review): default to Astra and CLI 0.163.0

[absorbb]

Set the shared AI review defaults to Codex CLI 0.163.0, model gpt-6-astra, and high reasoning effort (already the effort default). Update reusable/manual inputs, direct-event fallbacks in both jobs, documentation, and default contract assertions.

Retain the independently pinned codex-action v1.11 commit: CLI 0.163.0 already completed both structured and native review benchmarks with that action. Astra token usage is recorded; cost estimation remains unavailable until Astra-specific pricing is configured. Consumers pinned to an older workflow release must bump their release to adopt these defaults.

Validation: all 33 unit tests pass; actionlint and git diff --check pass; fresh local review found no issues.

[jitsu-code-review]

Review of 9e82a9024f3c6bd43bd59ead33687ac718795776

Reviewed the full diff and relevant execution paths. No high-confidence defects found. All 33 unit tests and git diff --check passed; actionlint was unavailable.