docs: revise pid_heat windup plan to pid_outer/pid_inner rename + Inner.Hold split

Supersedes the earlier flat yi_max clamp / FSM-gating ideas: same inner
PID instance switches its active param set (Inner.Heat vs Inner.Hold)
by state instead of freezing, giving bumpless transfer for free and a
tight yi_max that only applies while HOLD is driving it.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KefnwbGDM8CGrhb4sFhVq9

components/pid/TODO.md

@@ -73,11 +73,18 @@ git history for `temp_controller.py`/`temp_controller_smith.py`).
   clamp was considered and rejected: sustaining a genuine 1.5 K/min ramp
   needs `y≈0.7-0.75` from `yi` alone at steady state, the same range the
   disturbance itself peaked at, so no single clamp value can suppress the
-  windup without also capping legitimate ramps. Plan is instead to gate
-  `pid_heat`'s activity by FSM state (frozen/offline while `HOLD`, engaged
-  by command or a new `HoldHeatEngage` threshold) — see
-  `docs/overshoot_hold_windup.md` for the full writeup, open design
-  question (threshold relationship with `HoldHeat`), and test plan.
+  windup without also capping legitimate ramps. An FSM-gating alternative
+  (freeze the loop's output in `HOLD` unless engaged) was also superseded.
+  Current plan: rename `pid_hold`/`pid_heat`/`pid_cool` to `pid_outer`/
+  `pid_inner`/`pid_inner_cool` (matching what actually runs when), and
+  split the inner loop's config into `Inner.Heat`/`Inner.Hold`/
+  `Inner.Cool` so the *same* PID instance gets a tight `yi_max` only while
+  `HOLD` is driving it and stays unclamped for real `HEAT` ramps — no
+  freeze/thaw, bumpless transfer preserved for free. See
+  `docs/overshoot_hold_windup.md` for the full writeup and test plan. This
+  is also a breaking config change (`Hold`/`Heat`/`Cool` → `Outer`/
+  `Inner.*`) — every deployed `config.json` needs migrating, not just the
+  repo templates.
 
 - [ ] **`kalman.py` is now dead code in production.** Neither
   `temp_controller.py` nor `temp_controller_smith.py` uses `Kalman`