docs(agents): record the ~/.pylon-code runtime-home default

[rynfar]

Appends one record to .agents/durable-facts.jsonl for the decision shipped in #197: every Pylon server launch path (CLI, SSH remote launcher, WSL backend, dev runner) defaults its runtime home to ~/.pylon-code; ~/.t3 is never adopted as a fallback; --base-dir and T3CODE_HOME are unchanged overrides; the migration unit is userdata; the maintainer DB scripts refuse both homes.

Held back from #197 because the facts file only landed with #180. Append-only: no existing line touched, id unique, supersedes empty (no prior record stated the old default), all 14 source_paths and 10 source_commits verified against pylon.

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Claude Fable 5 in Pylon.

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[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	13.6 KiB	13.7 KiB	+173 B (+1.2%)	15.1 KiB	✅
Codex	Thread snapshot wire	6.9 KiB	6.9 KiB	−2 B (−0.0%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.6 KiB	6.8 KiB	+175 B (+2.6%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	57.2 KiB	58.7 KiB	+1.5 KiB (+2.6%)	66.4 KiB	✅
Codex	Live turn messages	10	11	+1 (+10.0%)	21	✅
Claude	Total thread wire	13.6 KiB	13.6 KiB	−9 B (−0.1%)	15.1 KiB	✅
Claude	Thread snapshot wire	6.9 KiB	6.9 KiB	−8 B (−0.1%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.6 KiB	6.6 KiB	−1 B (−0.0%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	58.1 KiB	58.1 KiB	0 B (0.0%)	66.4 KiB	✅
Claude	Live turn messages	10	10	0 (0.0%)	21	✅

Baseline: 2ff36ad · PR result: 298f148 · 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: 109.5 KiB
• Claude decoded thread snapshot: 110.2 KiB

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