feat(orchestrator): soft occupancy threshold requests handoff early (S11 partial)

Coordinator.Soft (default 0.55, ORCHESTRA_OCCUPANCY_SOFT) makes rotate()
and TurnDecision request a handoff advisory-only once occupancy crosses
the soft threshold, well before Hard forces a release/rotation.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01W1rkJ2hBMybnJctPbcy4tT

progress.md

@@ -273,8 +273,17 @@ Fixed so far:
   correct admit token accepted, same-id-different-token rejected as a
   hijack, same-id-same-token (legitimate restart) still succeeds.
 
-Not yet started: Codex/opencode Stop-hook-equivalent scripts, S8, S11. See
-`AUDIT.md` for the full plan.
+- **S11 (partial — soft threshold only)** — added `Coordinator.Soft`
+  (default 0.55, `ORCHESTRA_OCCUPANCY_SOFT` override). Both `rotate()` and
+  `TurnDecision` now request a handoff once occupancy crosses `Soft`, well
+  before `Hard` forces one; `TurnDecision` returns `prepare_handoff` for this
+  advisory case without requiring a turn boundary, leaving the task leased.
+  Covered by a new `TestTurnDecision` subtest. **Not done:** milestone
+  rotation, thrash detection, agent-initiated `ROTATE` — see AUDIT.md's S11
+  section for why those are bigger than a threshold check.
+
+Not yet started: Codex/opencode Stop-hook-equivalent scripts, S8, S11's
+milestone/thrash/agent-`ROTATE` pieces. See `AUDIT.md` for the full plan.
 
 **Phase 0 done (2026-07-27):** this box has live TCP reachability to the real
 herdr instance at `192.168.1.105:9245` — verified by hand (raw JSON-RPC