docs(dox): optimize root AGENTS.md (−49.5% lines / −38.8% bytes)

[edheltzel]

Summary

Optimizes the root `AGENTS.md` agent context while keeping the binding DOX rail intact. Two logical changes land together in one PR:

1. DOX rollout baseline (`57f57b7`) — captures the in-flight DOX framework rollout as a clean baseline.
2. AGENTS.md optimization (`231ef07`) — slims the root context file.

What changed

• Root `AGENTS.md`: −49.5% lines / −38.8% bytes. The verbose project-structure file tree is replaced with a directory-purpose map that points agents at `codegraph` and `fd` for live structure instead of a hand-maintained tree that drifts.
• New `docs/agents/dox-framework.md`: the DOX procedure is extracted here, with codegraph guidance woven into the Read-Before-Editing and Closeout steps (never assume structure codegraph can answer).
• `docs/AGENTS.md`: child DOX index updated to reference the new framework doc.
• Binding rail kept inline: project-wide instructions and the top-level Child DOX Index remain in root `AGENTS.md` — only the procedural detail moved.

Rationale

The root context file is loaded into every agent session; trimming drift-prone duplication (the file tree) and relocating procedure to a referenced doc reduces token cost without weakening any DOX contract.