docs: document workers and local rule trust flow in AGENTS.md

[boldsbrainai]

Summary

AGENTS.md is the canonical reference for AI agents and contributors, but two critical subsystems are undocumented:

1. Workers — warm-up-worker.ts, parse-worker.ts, cache-write-worker.ts: their responsibilities, message protocol, and when each is spawned are not described.
2. Local Rule Trust Flow — the pending → review → approve → reload lifecycle is not explained anywhere, making it opaque for contributors testing custom rules.

Fix

Add two sections to AGENTS.md:

• ## Workers — describe each worker, its message contract, and lifecycle
• ## Local Rule Trust Flow — document the trust state machine with a short example

Effort estimate

~2 hours

[KunjShah95]

can i work on these

[aymenfurter]

Sure, go ahead and raise a PR with an AGENTS.md. Please include links to the relevant docs so the model is aware of the existing markdown files. Let's keep it between 200–500 characters.