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/rows.py

@@ -40,8 +40,11 @@ def why_key(winner: str, claims) -> str:
 def tariff_plan_row(plan, tick_words: str, *, age_s, horizon_h: float,
                     provider: bool, max_age_s: float) -> str:
     """The *Tariff* status row: the 30 s tick's sentence AND the provider plan
-    (TARIFF-11), each with its own clock. "No plan" is said aloud on a site
-    that configured a provider. DECISIONS/MAIN-orchestration.md."""
+    (TARIFF-11): two sources, two clocks, and the row says so. The plan is
+    stamped with its own age from `tariff_at` (not moved on a kept plan,
+    TARIFF-12), up to TARIFF_MAX_AGE_S (5400 s); `age_s` is the caller's
+    measurement. "No plan" is said aloud on a site that configured a provider.
+    DECISIONS/MAIN-orchestration.md."""
     # UX-08: plain words, every figure kept. The tick's sentence is "now"; the
     # plan carries its own age.
     if plan is None:
@@ -55,9 +58,12 @@ def tariff_plan_row(plan, tick_words: str, *, age_s, horizon_h: float,
 
 def arbitrage_row(*, on: bool, decision, decided_at, cycle_at, now,
                   why: str) -> str:
-    """The *Arbitrage* status row: off, armed with no decision this cycle
-    (`why` is the loop's reason), or a decision with its age (TARIFF-11).
-    `on` is read from the options, never inferred from `decision is None`.
+    """The *Arbitrage* status row: three states (TARIFF-11): off (not armed),
+    armed with no decision this cycle (`why` is the loop's reason), or a
+    decision with its age.
+    `on` is read from the options, never inferred from `decision is None`:
+    `cycle()` returns at the input hold before `self.arb = None`, so the old
+    row named an option that was ON. The age is always printed, even 0.
     DECISIONS/MAIN-orchestration.md."""
     # UX-08: plain words; the setting is named by its label.
     if not on: