Docflow report frontmatter + anchorized outputs

[mikemol]

Summary

Generated reports must be docflow-compliant (frontmatter + anchors + section pins). Add reusable renderer and update emitters, then regenerate docflow reports.

Scope

• Shared report renderer (frontmatter + doc_sections + anchors).
• Update report emitters to use renderer.
• Docflow audit output includes frontmatter-wrapped reports.

Files (expected)

• src/gabion/analysis/report_markdown.py
• src/gabion/analysis/report.py
• scripts/audit_tools.py
• scripts/docflow_*.py
• out/docflow_*.md

Acceptance Criteria

• All emitted reports are docflow-compliant.
• Docflow audit passes clean.
• Anchors stable across re-emits.