[codex] fix CLI validation and repo hygiene

[Hanjo92]

Summary

• Add regression coverage for missing CLI option values and invalid --repo-path inputs.
• Fix CLI argument validation and repo path handling so failures are concise user-facing errors.
• Add CI, GitHub templates, release/community docs, lockfile, and include docs/ in npm package contents.

Root Cause

• The manual argument parser consumed the next token without checking whether it was another flag.
• Repo context ingestion called readdirSync before validating that an explicit repo path was a directory.

Verification

• npm ci
• npm test
• npm run smoke
• npm pack --dry-run

Addresses #7.