checks: generate CIMC support from release notes

[monrog2]

Summary

• add a release-time scraper for model-specific CIMC support in Cisco APIC release notes
• embed generated support data in the standalone validator so APIC execution remains deterministic and offline
• resolve the APIC-L3/M3 CIMC 4.1(1g) false failure reported in CIMC 4.1.1g and ACI 6.1.5e validation fails #435
• add parser safeguards, regression coverage, and maintainer workflow documentation

Scraper safeguards

• normalizes dotted and parenthesized CIMC versions
• maps every APIC model group named in shared release-note entries
• excludes explicitly deferred releases
• rejects unexpected unqualified CIMC entries
• enforces expected models and minimum version counts per model to detect incomplete source changes
• provides --check mode for release preparation

Validation

• python3 -m pytest -q: 1059 passed
• Python compilation passed
• live scraper freshness check passed
• git diff --check passed

Fixes #435