Proof - Collaborative Markdown Editor

Proof is a collaborative document editor for humans and agents. It supports two modes:

1. Web API - Create and edit shared documents via HTTP (no install needed)
2. Local Bridge - Drive the macOS Proof app via localhost:9847

Identity and Attribution

Every write to a Proof doc must be attributed. Two fields carry the agent's identity:

• Machine ID (by on every op, X-Agent-Id header): ai:compound-engineering — stable, lowercase-hyphenated, machine-parseable. Appears in marks, events, and the API response.
• Display name (name on POST /presence): Compound Engineering — human-readable, shown in Proof's presence chips and comment-author badges.

Set the display name once per doc session by posting to presence with the X-Agent-Id header; Proof binds the name to that agent ID for the session. These values are the defaults for any caller of this skill; callers running HITL review (references/hitl-review.md) may pass a different identity pair if a distinct sub-agent should own the doc. Do not use ai:compound or other ad-hoc variants — identity stays uniform unless a caller explicitly overrides it.

Human-in-the-Loop Review Mode

Human-in-the-loop iteration over an existing local markdown file: upload to Proof, let the user annotate in Proof's web UI, ingest feedback as in-thread replies and agreed edits, and sync the final doc back to disk. Two entry points, identical mechanics — load references/hitl-review.md for the full loop spec (invocation contract, mark classification, idempotent ingest passes, exception-based terminal reporting, end-sync atomic write) in either case: