docs(opc): make first success machine-verifiable

[runesleo]

Why

External-agent usability testing found the public first-success path was runnable but not machine-verifiable from docs alone.

What

• add clean-checkout clone entry point
• state Git + Python 3 / stdlib-only requirements
• define exit-code contracts for reject/pass cases
• define exact output tokens for status, verify, failover and continuation
• add cwd/path guidance
• keep Chinese and English README aligned

Evidence

• clean checkout machine path: PASS
• external Grok Round1: insufficient / public_docs_alone=false
• docs-only fix
• local contract: 8/8 PASS
• same Grok Round2: pass / remaining_blockers=[] / public_docs_alone=true

No verifier logic, production topology, private prompts, credentials, scheduler bindings, wallet/trading data, or exact quota routing are included.