Add Symphony to Usage & Observability

[itsloganmann]

Adds Symphony, a live dashboard and 3D repo map of the AI coding agents working across a team.

• Hooks stream every file edit from Claude Code, Codex, and opencode into Supabase; the board updates in real time with per-person cards, collision flags for overlapping edits, and a token leaderboard.
• Self-hosts locally or on Modal with a free Supabase project. MIT, Python/FastAPI.

Placed at the end of Usage & Observability to respect the star-count ordering.

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