Extracted 7 helper methods from RenderMarkdown (132 lines, CC=21). No behavior changes.

Changes:
- renderHeader, renderScoreBreakdown, renderDetectorResults
- renderSecretScan, renderVulnScan, renderIssues, renderFooter
- Fixed backslash escaping regression (\\n -> \\n)
- CI: scan only changed files, pin AILINTER version, fix GITHUB_OUTPUT

… short/mid/long-term goals and community milestones

Replaces the minimal phase-checklist roadmap with a detailed
document covering:
- Current shipped capabilities (20 quality detectors, 269+ secret
  rules, 58 vulnerability patterns, 24 refactoring strategies, MCP
  server, VS Code extension, CI/CD integrations)
- Short-term Q3 2026: Python support expansion, CI/CD depth,
  community outreach, platform polish
- Mid-term Q4 2026: JS/TS and Rust support, JetBrains/Neovim plugins,
  parallel scanning, MCP v2
- Long-term H1 2027: Custom rule engine, team collaboration,
  enterprise SAML/SSO, GitHub App, AI agent ecosystem
- Community goals: 100+ stars, 10+ contributors, 5+ integrations

…ault (#14)