feat(grafiphy): add ELI5 pseudocode diagram generation for PR reviews

[ChonSong]

Summary

Add grafiphy module that generates ELI5 pseudocode diagrams for PR reviews using real graphify data.

What's New

• grafiphy/orchestrator.py — Coordinates renderers, labeler, and GitHub upload
• grafiphy/labeler.py — Template-based label generator with strict format rules
• grafiphy/renderers/sankey.py — Flow/pipeline diagrams (matplotlib)
• grafiphy/renderers/mermaid.py — Sequence/call-flow diagrams (Playwright + Mermaid.js)
• grafiphy/renderers/architecture.py — System topology diagrams (matplotlib)
• grafiphy/renderers/graphify_tree.py — Dependency tree screenshots (Playwright)

Label Rules (Strict)

1. Every label MUST include exact code names in backticks
2. "(not Z)" ONLY for real decisions visible in code
3. Edges: "sends X to Y" (payload + target)
4. 5-8 words per label

Integration

• Companion calls grafiphy on PR events when COMPANION_ENABLE_DIAGRAM=1
• Diagrams uploaded to GitHub release assets
• Embedded in TL;DR comments as Markdown images

Testing

Tested end-to-end on PR #73 (hermes-webui-extensions). See comment: hermes-webui/hermes-webui-extensions#73 (comment)

Summary by CodeRabbit

• New Features
  • PR reviews can now include a single Excalidraw-style diagram summarizing code flow and relationships.
  • Review automation can add inline suggestions and structured review summaries.
• Bug Fixes
  • Updated reaction GIFs now provide distinct animations for supported review categories.
  • Improved handling of incomplete issue-comment metadata.
• Improvements
  • Automated reviews avoid repeating work for the same change or within a 24-hour window.
• Documentation
  • Added documentation describing diagram generation and review integration.