docs: tighten Codex agent rules

[fall-out-bug]

Summary

• replace generic Codex guidance with sdp_lab-specific orientation
• list evidence-backed Go/SDP commands and mark non-existent generic gates as not found
• document generated adapter boundaries and verification labels

Verification

• git diff --check -- .codex/AGENTS.md

Not assessed

• Go quality gates; documentation-only Codex guidance change

[github-actions]

SDP Auto-Attestation

Field	Value
Branch	codex/sdp-lab-codex-rules
Commit	1940c646
Changed files	1
Tests	✅ pass (6129 passed, 0 failed)
Lint	✅
Scope	✅ no linked workstreams — auto-attested from CI observation
Attestation generation	✅
Coverage	⚠️ 65.28714285714287%
Signed	✅ Sigstore bundle
Beads	sdplab-t5k3

Full attestation report

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Generated by SDP auto-attestation