MAINT-21 round 2: keep the move pure - revert the added DECISIONS text, restore cut comments

Router T241: the comments commit had put new rationale into
MAIN-orchestration.md and cut comment lines that the note at 56fc41f did not
hold.

- DECISIONS/MAIN-orchestration.md is the 56fc41f text plus the one sentence
  that the Controller is split into app/main.py and app/ctl_*.py.
- Comments whose content is not in a DECISIONS note at 56fc41f are back in the
  code verbatim: MAINT-05 one config, the SAFETY-02, SAFETY-42/34,
  SAFETY-30 site half, SAFETY-31 and SAFETY-18 latch blocks in __init__, the
  _grade_store_migration docstring and comment, the trade_power_w docstring,
  the rows.py docstrings.
- Kept: cuts of text already in the note, the SMA-10 / SAFETY-137 / SMA-2
  pointers, the SAFETY-32 line fix.

No code change: maint21_same_ast OK, maint20_same_code -OO same.

Co-Authored-By: Claude <noreply@anthropic.com>

goodwe_controller/app/ctl_trade.py

@@ -82,10 +82,14 @@ MAINT_CHARGING_W = 50.0
 
 class TradeMixin:
     def trade_power_w(self, floor_pct, ceiling_pct) -> tuple:
-        """OPT-09. `(charge_w, discharge_w)`: how hard a trade may be SIZED,
-        on arbitrage's own SoC bounds, not the BMS cut-out. A pack whose SoC
-        did not read counts on neither side; neither side may be zero on a
-        trading tick (`IDLE_NO_SIZE`). DECISIONS/MAIN-orchestration.md."""
+        """OPT-09. `(charge_w, discharge_w)`: how hard a trade may be SIZED:
+        what the site can push AND STILL HAVE SOMEWHERE TO PUT. The bounds are
+        arbitrage's own (`arbitrage_soc_floor` / `_ceiling`), NOT the BMS
+        cut-out that `packshare.envelope()` uses (SAFETY-25): different
+        questions. It sizes the ask, it does not route it. A pack whose SoC did
+        not read counts on neither side. Neither side may be zero on a trading
+        tick (`arbitrage.decide()` refuses `IDLE_NO_SIZE`: a 0 W claim is a
+        park order). DECISIONS/MAIN-orchestration.md."""
         # The reduction lives in `packshare`; `test_packshare.py` part 9 calls
         # the SAME function (a transcription in a check is a copy that drifts).
         return packshare.trade_power_w(self.pack_energy, floor_pct, ceiling_pct)