Docs rewrite, dashboard polish, branching guide

[TomMaSS]

Summary

• Documentation rewrite — all 4 docs updated to technical writing standards with ToC, structured sections, accurate content reflecting current codebase
• Dashboard fix — tooltip readability (solid bg, bold labels, drop shadow) + sidebar status dot instant refresh on status change
• AGENTS.md — added Git Branching Strategy section with naming conventions and workflow rules

Docs updated

File	Key changes
data-model.md	Full ER diagram with all tables (project_members, audit, access_log, etc.), column-level detail, migration file reference
tool-reference.md	32 tools (was 31), 6 workflow examples, token budget guide
scaling.md	Reflects current Better Auth + RBAC, WebSocket scaling, production checklist
token-stats-metrics.md	New file — comprehensive metrics reference for Stats dashboard

Test plan

• npx tsc --noEmit — typecheck clean
• Status dot updates immediately on change (no reload needed)
• Tooltip readable on dark background (solid card color, bold labels)
• All docs render correctly in GitHub markdown preview