OPT-09: the weights parameter nothing ever passed, and what it cannot do

`allocator.plan()` has taken a `weights` argument since ALLOC-01 and NOTHING
had ever passed one - main.py called `resolve()` without it and the arbiter
defaulted it to 1.0 per unit - so the site target was split 50/50 regardless
of what either pack could do. Two things now feed it, and they are different
kinds of thing:

  * a `pack` UNIT claim at P_SAFETY that CLOSES a unit's envelope at its own
    `bms_soc_floor` or at 100 % - a PERMISSION, obeyed absolutely, so an empty
    pack is not asked to discharge and its share goes to the sibling;
  * SoC-aware weights by ENERGY headroom in kWh - a PREFERENCE, which
    `_fill()`'s last-resort pass will override the moment the sibling saturates.

Measured (test_packshare.py part 8): at a load one pack cannot cover, the
weighted arm and the shipped arm command the IDENTICAL watts into an empty pack
and deliver the IDENTICAL watts. Only the envelope stops the ask, and what it
buys is not delivery - it is a reported `unmet_w` where the record used to read
impeccable. Weights are a comfort choice for STABILITY and NOT for DELIVERY.

Also: an optional per-entry `capacity_kwh` (schema change, all-or-nothing across
the roster, rule 9 refuses a partial one); per-pack arbitrage sizing, with the
sell side's no-op stated rather than hidden; and a 0 W trade refused by name,
because a 0 W arbitrage claim is a park order that outranks the loop.

SAFETY-42 and this card meet at one hazard from opposite sides - OPT-09 stops
the site ASKING a pack whose SoC says it cannot deliver, SAFETY-42 alarms when a
pack that said it could does not - and its end-to-end fixture moved as a result.
Its finding is unchanged and is now stated on the two quantities its rejected
discriminator actually reads.

Not filed at all at a roster of one: at N=1 every source routes to the site, so
the interval would bound the SITE TARGET, and SAFETY-25's decided Option A
stands untouched on the live install.

⚠️ INVERTER B DOES NOT EXIST. Its 4600 W / 20.48 kWh / 10 % are FROM DATASHEET
AND SERIAL, and `sim/plantsim.py`'s INVERTER_B is inverter A copied
(`measured=False`), so every two-inverter figure here is arithmetic or two
copies of A. No hardware was touched.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BwRLw7eKYj2byVdwB6kbjU

goodwe_controller/app/arbitrage.py

@@ -173,6 +173,17 @@ IDLE_NO_SOC = (
     "state of charge is not being read, and a battery whose fill nobody knows "
     "cannot be told to empty or to fill")
 IDLE_OFF_PEAK_HOUR = "this hour is neither the buy hour nor the sell hour"
+# OPT-09. A TRADE NOTHING CAN TAKE IS NOT A TRADE, AND THE ALTERNATIVE IS WORSE
+# THAN A MISSED HOUR. `charge_w`/`discharge_w` used to be the site's whole rating
+# and are now SIZED to the packs whose state of charge permits that direction, so
+# a caller can hand this function a zero. A zero must not reach `claim()`: a
+# `Claim.set(..., 0.0)` at P_ARBITRAGE is a PARK ORDER that outranks the loop,
+# which is the failure the note on `claim()` is written against - it would
+# silently disable self-consumption for the whole hour. So the sizing is checked
+# where the decision is made rather than trusted to arrive positive.
+IDLE_NO_SIZE = (
+    "no pack's state of charge permits this side of the trade, so it is sized "
+    "at 0 W - and a 0 W arbitrage claim is a park order, not a trade")
 NEGATIVE_PRICE = (
     "§17: the sell hour is priced BELOW ZERO, so discharging into it would give "
     "energy away and pay for the privilege. Arbitrage must not export at a "
@@ -372,6 +383,8 @@ def _act(plan, now, v, soc, charge_w, discharge_w, floor_pct, ceiling_pct):
                 f"the sell hour is here at {price:.4f} EUR/kWh but the pack is "
                 f"at {soc:g} %, at or under the {floor_pct:g} % reserve floor "
                 f"arbitrage may not spend (§10.1 priority 4)", **common)
+        if not abs(float(discharge_w)) > 0.0:
+            return _idle(IDLE_NO_SIZE, **common)
         return ArbitrageDecision(
             action=DISCHARGE, power_w=abs(float(discharge_w)),
             reason=(f"{DISCHARGE}: this is the dearest firm hour at "
@@ -388,6 +401,8 @@ def _act(plan, now, v, soc, charge_w, discharge_w, floor_pct, ceiling_pct):
             f"the buy hour is here at {price:.4f} EUR/kWh but the pack is at "
             f"{soc:g} %, at or over the {ceiling_pct:g} % ceiling - there is "
             f"nowhere to put the cheap energy", **common)
+    if not abs(float(charge_w)) > 0.0:
+        return _idle(IDLE_NO_SIZE, **common)
     return ArbitrageDecision(
         action=CHARGE, power_w=-abs(float(charge_w)),
         reason=(f"{CHARGE}: this is the cheapest firm hour at "