Require synthetic disposable fixtures in agent test guidance

[nullStack65]

AGENTS.md now requires meaningful synthetic data in fresh, owned disposable fixture directories. It removes instructions to snapshot real userdata, delete destination SQLite files, or copy credentials/settings into tests, and preserves separately authorized read-only inspection. Cleanup is limited to owned fixtures and processes. The change also links the landed canonical HUMANS.md guide.

Exact reviewed source: 47a4f58a8b2ab1f235118fd686a31a713a4ebedf; base 23467c599a401b7a5baf3c7052f0d45a181bc278. Only AGENTS.md changes.

Validation: independent corrected-head read-only review PASS with no findings (report SHA256 033ac71d3d095402bc2e711976aad11876880f0e1e47d37abef47c96e555249e); diff checks passed. Normal CI Check, Test, Server 1/2/3, Rust and Release Smoke succeeded. The earlier cancelled native-fingerprint run was superseded by same-head success; path-filtered skips are not test passes. No broad tests were repeated for the documentation-only review.

This is source guidance. Installed-harness propagation and effective behavior remain separate delivery obligations. No production data, credential, database or runtime changes are included.

[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	13.5 KiB	13.5 KiB	−5 B (−0.0%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.1 KiB	7.1 KiB	−4 B (−0.1%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.4 KiB	6.4 KiB	−1 B (−0.0%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	56.2 KiB	56.2 KiB	0 B (0.0%)	66.4 KiB	✅
Codex	Live turn messages	9	9	0 (0.0%)	21	✅
Claude	Total thread wire	13.5 KiB	13.5 KiB	+5 B (+0.0%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.1 KiB	7.1 KiB	0 B (0.0%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.4 KiB	6.4 KiB	+5 B (+0.1%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	57.0 KiB	57.0 KiB	0 B (0.0%)	66.4 KiB	✅
Claude	Live turn messages	9	9	0 (0.0%)	21	✅

Baseline: 23467c5 · PR result: 47a4f58 · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 113.9 KiB
• Claude decoded thread snapshot: 114.6 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.