docs: publish-train rules — coupled-release gates codified (option-2)

manifest-before-floor; floor field LAST (hub_settings DB row overrides env, acts
immediately — the 0.81/0.113 9-minute skew incident); MinAgent fleet gate
(controller CHANGELOG header convention from ctrl v0.114.0); the controller
capability gate as box-level backstop.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PSK5g6qYLknKj8u3QAFEr6

CONTEXT.md

@@ -3,6 +3,15 @@
 > Created with the REUSE.md rollout (2026-07-03). Authoritative history: `hub/CHANGELOG.md` (hub),
 > `website/CHANGELOG.md`, `scripts/CHANGELOG.md`; end-of-task detail in `REPORT.md`.
 
+- **2026-07-11 — PUBLISH-TRAIN RULES CODIFIED** (`documentation/runbooks/publish-train-rules.md`,
+  option-2 of the skew answer): 1. manifest before floor; 2. the manifest screen carries the LIVE
+  DB floor (`hub_settings.min_controller_version` overrides env, acts immediately) — save the floor
+  field LAST; 3. MinAgent fleet gate (controller CHANGELOG header convention from ctrl v0.114.0;
+  floor may not rise past an unmet MinAgent — hub dashboard check, manual at current fleet size;
+  hub-enforced per-box gating = deferred option-3); 4. box-level backstop = controller v0.114.0's
+  agent-capability gate (route probe, felhom-controller `internal/agentapi/features.go`). Hub
+  UNTOUCHED (floor-UI separation = its own future task).
+
 - **2026-07-11 — PUBLISH TRAIN 0.81/0.113 COMPLETE — PETI LIVE on agent 0.81.0 + controller 0.113.0.**
   Record: `documentation/pilot/RUNBOOK-publish-0.81-0.113-2026-07-11.md`. Agent 0.81.0 published
   (sha `914bb3b5…30df0b`, live-bytes, anon-verified) + golden 0.113.0 baked/published (sha