docs(openclaw): `docs/openclaw-deploy.md` — drop vouch into a deployment in 5 minutes

[plind-junior]

What you're trying to do

The README has a small "Running vouch as an OpenClaw plugin" section. A reader who wants to actually deploy needs a walkthrough: pre-reqs, enable command, what the trust boundary looks like at runtime, how to debug a misload, how to verify the plugin landed. Five short steps with copy-paste blocks.

Suggested shape

docs/openclaw-deploy.md with these sections, each one paragraph + one code block:

1. Prereqs — OpenClaw ≥ 2026.4, vouch-kb ≥ 0.1.0, a python on PATH.
2. Enable — openclaw plugin add vouchdev/vouch + openclaw plugin enable vouch.
3. Verify — openclaw plugin list shows vouch as enabled, loaded.
4. Trust check — every write goes through the review gate; explicit example.
5. Debug — common misloads, where to find vouch's log line in OpenClaw's loader output.

Acceptance

• The walkthrough takes a fresh OpenClaw deployment to a working kb.search call in <5 minutes (verified by a contributor following only the doc).
• Cross-linked from README's OpenClaw section + AGENTS.md.

Out of scope

• Multi-tenant deployment patterns (single-tenant first).
• Production hardening checklist (sibling doc).