docs: convert remaining ASCII diagrams to Mermaid + add Mermaid rule to CLAUDE.md
ARCHITECTURE.md:
- System Overview → flowchart (React Frontend / Rust Backend / External Services)
- MCP Server Architecture → flowchart (index.js, vault.js, ws-bridge, transports)
- WebSocket Bridge → flowchart LR (Frontend ↔ ws-bridge ↔ vault)
- Vault Cache Three Strategies → flowchart (full scan / incremental / cache hit)
- Auto-Save Flow → flowchart LR
- Git Sync Flow → flowchart TD (auto-sync + manual commit paths)
CLAUDE.md:
- Added 'Documentation Diagrams' section: Mermaid preferred for all new diagrams,
convert ASCII on sight, exception for spatial wireframe layouts
2b33536a68