feat: discover Claude Code project instructions

[CoderDeltaLAN]

Summary

• Discover Claude Code project instructions at .claude/CLAUDE.md.
• Add fixture and regression coverage for the supported path.
• Update README/RULES/CHANGELOG so supported paths, normal CLI use, development venv setup, Ruff/dev dependencies, local checks, and next-release audit readiness are explicit.

Verification

• Focused discovery and fixture tests pass.
• Full local check passes from a temporary development virtual environment with .[dev].
• Branch diff scope and secret-pattern scan were checked before push.