DEV-02: per-instance inverter objects, so nothing is graded against a sibling

Every piece of per-device state in the Controller was a scalar, and several of
them are safety inputs. app/inverter.py introduces an `Inverter` that owns its
entities, its rating, its device range, its SignWatchdog, its last_write and
its last_beat, under store keys namespaced by unit name. The Controller holds a
list of them and keeps only what is genuinely site-level: the P1 reading, the
site integrator, and the tariff quarter.

WHAT THE SCALARS WERE SILENTLY ASSERTING

  dev_min/dev_max   one pair, read from one setpoint_entity. A second
                    inverter's rating was NEVER READ AT ALL, so its clamp, its
                    freeze rail and the peak guard's achievable_w were the
                    first one's numbers.
  soc               one reading into the maintenance FSM, SAFETY-24's pack
                    floor and arbitrage's bounds. An average lets the emptier
                    pack be driven below its own floor.
  sign_wd           ONE SignWatchdog, whose own docstring says "one instance
                    per actuator", latched under FLAT store keys - so a trip
                    caused by B latched A across restarts and one operator
                    press cleared both.
  last_beat         one deadline and one serialised hass.call(), so a hung
                    write to A ate B's 30 s layer-1 budget.

actual_w BECAME SITE LEVEL WHILE THE READINGS BECAME PER-INSTANCE, and those
are opposite directions on purpose. compute()'s anti-windup test is
`abs(prev_w - actual_w) > saturation_w` with prev_w the SITE target, so feeding
it one inverter's power compares a site number against a unit number, trips the
saturation freeze permanently and leaves a standing grid error. Measured on
admin/goodwe's two-master rig (tools/alloc_sim.py --splits, 2 kW load, 40
cycles), worst |delta| between splits at the meter:

    gain    one unit's power      the site sum
    0.2           510 W                0 W
    0.4           250 W                0 W
    0.6            50 W                0 W

That was ALLOC-01's disclosed finding; test_alloc.py part 8 kept its stimulus
and now grades the other row.

THE STORE MIGRATION IS GRADED, NOT MERELY PERFORMED. sign_tripped/sign_reason
move to unit/<name>/... once, verified by READING BACK what was written, and
the version marker is set only when nothing that carried state was lost. The
flat keys stay in the file so a rollback still finds its latch. And __init__
compares the pre-migration flat latch against what unit A actually came up
with: if the latch did not survive it is RE-ARMED from the legacy value and
shouted about. A latch that silently fails to migrate is a disarmed safety
guard on an install whose state file says it is protected - which is strictly
worse than never persisting it, because now there is evidence saying it is
fine. test_inverter.py part 2 breaks the migration and watches the guard fire.

HEARTBEATS ARE INDEPENDENT AND THE BUDGET IS DERIVED. Each inverter owns its
deadline, the refreshes go out concurrently, and each write is bounded by
WRITE_BUDGET_S = 4 s. The inequality is graded rather than asserted: 4 +
heartbeat_s's schema maximum of 25 < 30, validate.FIRMWARE_INGEST_VETO_S.
Verified by injecting a transport that accepts and never answers.

live_units() ANSWERS HONESTLY. A unit whose every write has been rejected for a
whole layer-1 window is not commandable; the allocator drops it, the survivors
carry its share, the action log names it, and the dropped unit is commanded
0 W rather than left standing on its last share. A roster entry with NO
setpoint_entity is deliberately not handled there - that is a configuration
that cannot be delivered, and it reaches main.py's refusal branch, which is how
that branch keeps a live trigger after this card removed its old one.

AT N=1 NOTHING MOVES. The removed scalars survive as read/write properties of
the sole inverter, so every existing replay runs unmodified - and they REFUSE
at N>=2 rather than answering for the first inverter, which is the tripwire on
a consumer that was never made per-instance.

EVIDENCE. 19 files green. test_inverter.py is new (82 checks). Eighteen
mutations were applied to the shipped modules on a purged tree via
tools/mutation_run.sh and each was observed RED. Two of them SURVIVED first
time and the checks were changed rather than the table: the serialised dispatch
and the shared last_beat both passed while part 6 gathered its own writes and
computed its own `due` list. send_heartbeats() was extracted from run_control()
so the shipped dispatch is reachable by a check at all.

INVERTER B STILL DOES NOT EXIST. build_roster() returns exactly one inverter
from the flat options and is the one function CFG-04 changes; every two-unit
figure here is architecture, and the second rating in the checks is marked a
hypothesis.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BwRLw7eKYj2byVdwB6kbjU

goodwe_controller/tools/alloc_sim.py

@@ -6,6 +6,11 @@
     python3 tools/alloc_sim.py --sweep       # AC 3: gain to 1.0 at every split
     python3 tools/alloc_sim.py --all
 
+    # DEV-02: the split-invariance finding ALLOC-01's review handed on, and the
+    # sensing change that closed it. The two rows are the evidence.
+    python3 tools/alloc_sim.py --splits --gain 0.4 --feedback unit   # 250 W apart
+    python3 tools/alloc_sim.py --splits --gain 0.4 --feedback site   # identical
+
 WHY THIS IS A SCRIPT AND NOT A `test_*.py`
 ==========================================
 It needs admin/goodwe checked out beside this repository, and the add-on's CI
@@ -121,20 +126,28 @@ def run_site_feedback(sitesim, control, mode, gain, load_w=2000.0, cycles=40,
                       cycle_s=None, dt=0.05):
     """`sitesim.run_site()` WITH EXACTLY ONE LINE CHANGED, and it is named here.
 
-    ⚠️ THIS IS A COPY AND IT IS A COPY ON PURPOSE. `run_site` feeds `compute()`
-    ONE inverter's power as `actual_w`, and its docstring says why: the shipped
-    add-on binds a single `inverter_power` sensor, so an operator who wires up a
-    second inverter has a loop that sees unit A only, and a rig that fed the sum
-    would be KINDER than the deployment. That is correct for grading the
-    broadcast fault and it is exactly the variable this experiment has to move,
-    because it is the one input to the loop that is a function of the SPLIT.
+    ⚠️ THIS IS A COPY AND IT IS A COPY ON PURPOSE. `run_site` lives in
+    admin/goodwe, which this file reads and never writes, and it feeds
+    `compute()` ONE inverter's power as `actual_w` because that is what the
+    add-on gave it: a single `batt_entity`, so an operator who wired up a second
+    inverter had a loop that saw unit A only. A rig that fed the sum would have
+    been KINDER than the deployment.
 
     So this differs from `run_site` in one expression - `site.battery`, the
     site's total inverter power, instead of `inverters[0].plant.actual` - and in
-    nothing else. It is not evidence about the shipped add-on; it is the
-    counterfactual that says WHICH of the two candidate causes explains the
-    split-dependence that `--splits` measures at gain 0.6. The add-on does not
-    have this sensor yet. DEV-02 is where it would come from.
+    nothing else.
+
+    ⚠️ AND SINCE DEV-02 THAT ONE EXPRESSION IS THE SHIPPED ONE, WHICH TURNS THIS
+    FUNCTION FROM A COUNTERFACTUAL INTO THE MODEL. `Controller.site_batt_w` is
+    the SUM of the per-instance battery readings and is what main.py hands
+    `compute()`; `--feedback site` is therefore the add-on as it now stands, and
+    `--feedback unit` is the PRE-DEV-02 sensing, kept because the comparison is
+    the evidence. Measured here, 2 kW load, 40 cycles: fed one unit's power the
+    aggregate trace at the meter is split-dependent by 510 W at gain 0.2, 250 W
+    at 0.4 and 50 W at 0.6; fed the site total every split is bit-identical at
+    every gain. `run_site` still models the old sensing and must not be
+    "corrected" to the new one - the row it produces is what the fix is measured
+    against.
     """
     from plantsim import INVERTER_A, INVERTER_B, Inverter, Site
     cycle_s = sitesim.CYCLE_S if cycle_s is None else cycle_s
@@ -240,10 +253,11 @@ def main():
     ap.add_argument("--load", type=float, default=2000.0)
     ap.add_argument("--gain", type=float, default=1.0)
     ap.add_argument("--feedback", choices=("unit", "site"),
-                    default="unit",
-                    help="what the loop is fed as actual_w: one "
-                         "inverter's power (the shipped add-on) or "
-                         "the site total (the counterfactual)")
+                    default="site",
+                    help="what the loop is fed as actual_w: the site total "
+                         "(the shipped add-on since DEV-02, the default here) "
+                         "or one inverter's power (the PRE-DEV-02 sensing, "
+                         "kept because the comparison is the evidence)")
     a = ap.parse_args()
     if not (a.table or a.splits or a.sweep):
         a.all = True