SAFETY-91: a held battery is drawn only after the others are full

At N>=2 a battery at or under its own peak reserve now weighs 0 whenever
the site gives (not only for the peak), a draining battery's pin becomes
a floor at its drain rate so it rises before the held one gives, and a
quarter's edge is graded on the next quarter when its first telegram is
late. SAFETY-25 option A stays: the held battery is still drawn once the
others are full. N=1 unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

goodwe_controller/test_modes.py

@@ -129,6 +129,19 @@ finally:
 # cd4d9cb5b7e29ff4ab4fe65dab5106683d8a599f09323fbdee4018ad9b28fcd1.
 SAFETY78_N2_MAINT = \
     "1afcd46b1b987868b110d2b0f4a7555848c9aa4728a836d4a2ce2a2107268497"
+# SAFETY-91 changes n2 and n2_off ON PURPOSE: from t=1600 battery A is at its
+# 20 % reserve, so B carries the house first and A gives last. With
+# `_held_back()` reverted to SAFETY-87's (held only for the peak) both are
+# a5dddad's again, which the check below grades.
+SAFETY91_N2 = \
+    "9535c08f556d6d50bec8fb0872445173480c29b10df1a7c437ef73d6ddb2814d"
+_real_hb = app_main.Controller._held_back
+app_main.Controller._held_back = lambda self: self._peak_reserve()
+try:
+    _n2_s87 = rig.digest(rig.run(**rig.SCENARIOS["n2"])[0])
+finally:
+    app_main.Controller._held_back = _real_hb
+_S91 = ("n2", "n2_off", "n2_maint")
 for k in A5DDDAD:
     print(f"    {k:7} {'same' if _now[k] == A5DDDAD[k] else 'DIFFERS'} "
           f"{_now[k][:16]}")
@@ -136,10 +149,14 @@ check("⭐ at N=1 and N=2, with the option absent and with it false, every "
       "command, reason and allocation record over 540 cycles each is "
       "byte-identical to a5dddad (house steps, a solar surplus, a battery "
       "at its cut-out level, at N=2 a refusal with probes, both batteries "
-      "due for maintenance; n2_maint apart, below), and so is the arbiter "
-      "on 6000 claim lists",
-      {k: v for k, v in _now.items() if k != "n2_maint"}
-      == {k: v for k, v in A5DDDAD.items() if k != "n2_maint"})
+      "due for maintenance; n2, n2_off and n2_maint apart, below), and so "
+      "is the arbiter on 6000 claim lists",
+      {k: v for k, v in _now.items() if k not in _S91}
+      == {k: v for k, v in A5DDDAD.items() if k not in _S91})
+check("...n2 and n2_off are the SAFETY-91 digest (A at its reserve gives "
+      "last), and SAFETY-87's held rule gives a5dddad's back",
+      _now["n2"] == _now["n2_off"] == SAFETY91_N2 != A5DDDAD["n2"]
+      and _n2_s87 == A5DDDAD["n2"])
 check("...and n2_maint is the SAFETY-78 digest: the N=2 drain that a5dddad "
       "refused on 392 of 540 cycles now runs (test_safety78.py), bounded by "
       "SAFETY-85",