feat: Add responsible disclosure generator (Phase 6.5)

New module scripts/disclosure_generator.py provides:
- Private disclosure report generation (full details)
- Public-safe issue templates (no exploit details)
- Automatic path sanitization (removes machine-specific paths)
- GitHub repo security option detection (SECURITY.md, Discussions)
- Disclosure timeline generation (14-day followup, 30-day public)
- GitHub Discussion creation for security contact requests
- Separation of code vulnerabilities vs dependency CVEs

Integration with hybrid_analyzer.py:
- New Phase 6.5: Responsible Disclosure Report Generation
- CLI args: --enable-disclosure-report, --disclosure-repo,
  --disclosure-reporter, --disclosure-create-discussion
- Environment variables: ENABLE_DISCLOSURE_REPORT, DISCLOSURE_REPO_URL,
  DISCLOSURE_REPORTER, DISCLOSURE_CREATE_DISCUSSION

Usage:
  python scripts/hybrid_analyzer.py /path/to/repo \
    --enable-disclosure-report \
    --disclosure-repo owner/repo \
    --disclosure-reporter "Security Team"

Or standalone:
  python scripts/disclosure_generator.py \
    --input findings.json \
    --output ./disclosure \
    --repo owner/repo

Author: devatsecure