SAFETY-32 fix round: grade the reduction on packs whose floors DIFFER

AC 6 was not met for the reduction main.py actually hands decide(). The
reviewer removed the per-pack grading twice and the 19-file suite stayed green
both times. No shipped behaviour changes here - app/ is untouched. What changes
is what observes it.

WHY BOTH SURVIVED, and it is this repository's recurring defect landing on this
card's own Decision 2: under any rule-8-valid config every pack's
pack_floor_pct() equals peak_soc_floor, so `floors` is a list of IDENTICAL
numbers and max/min/first/last are four spellings of one answer. The only check
using a cut-out ABOVE the EMS floor - 12c's `_n1_deep` - ran on a roster of ONE,
where every reduction agrees. So no check ever evaluated binding_soc_floor() on
two packs whose floors differ. And the degeneracy is not a defence: this PR's own
argument ("unreachable is a claim about today's rule ordering, and
validate_startup_config() is also sim/inject.py's entry point") justifies writing
the reduction and equally obliges grading it.

  * test_peakguard.py part 12c2 - NEW. binding_soc_floor() on a roster whose
    per-pack floors ALL DIFFER: four SIMULATED cut-outs 30/25/40/35 %, each
    strictly above peak_soc_floor, so max (40), min (25), first (30), last (35)
    and the mean (32.5) are five different numbers and the extremes sit at
    INTERIOR roster positions. Two packs structurally cannot separate those -
    there max==last and min==first - and neither can three; four is the smallest
    roster that can. Precondition is its own check (habit 1); the counterfactual
    raises ONE pack - the last, neither extreme - past the old maximum and the
    answer follows (habit 7); peak_soc_floor is then lifted above every cut-out
    to grade the other side of the conjunction.
  * test_peakguard.py part 12g - REWRITTEN as behaviour (habit 4). The old
    assertion was `"self.packs" in <the unparsed call site>`, which `self.packs[:1]`
    still satisfies. It now drives REAL Controller.cycle()s on a two-pack roster,
    both packs at the same SoC, and reads PeakDecision.soc_floor - the argument,
    echoed back by the shipped decide(). The cut-outs are the only thing varied,
    and the SAME PAIR is carried in BOTH ORDERS.
  * ⚠️ TWO MORE SURVIVORS, found by this round's own battery and recorded rather
    than quietly repaired. (a) The first cut of 12g varied only pack B's cut-out,
    so `self.packs[-1:]` (+5 bytes) agreed with the roster on both runs and stayed
    green across all 19 files; the swapped pair closes it, and between the two
    directions no single-position slice passes all three runs. (b)
    binding_soc_floor()'s EMPTY-roster branch rewritten to `return None`
    (-43 bytes) was green too - a defensive branch nothing in the suite reached.
    Both directions of it are pinned now.
  * wired_over_limit() gained a prepare(ctl) hook, inside its retry loop so every
    attempt grades the same site.
  * In-process mutation rows 22, 22b and 23 record all four survivors.

Nine further source mutations went through the harness on the fixed tree
(binding_soc_floor -> floors[0] / floors[-1], pack_floor_pct conjoining with
min, pack_permissions grading against packs[0], `any` -> `all` on the unknown
floor, Controller.packs reversed, decide(soc=) taking inverters[0].soc, and the
two survivors above). Seven were red on first run; the two survivors are now red
as well. Three of the nine have a ZERO byte delta and still went red, which is
the direction stale bytecode cannot fabricate - and the harness purged anyway.

MANDATORY PROOF, all in the CI image over a tree rsynced to a plain path and
bind-mounted :ro, bytecode entry count printed before and after the purge:
each of the four mutations now takes test_peakguard.py RED, and the unmutated
tree is 19/19 green (twice, plus test_peakguard.py five times in isolation -
card CI-06's flake did not reappear). The zero-byte one was proved to have RUN rather than
assumed: dis.get_instructions LOAD_GLOBALs were [float, pack_floor_pct, any,
min] and binding_soc_floor() returned 25.0 on the 12c2 roster where the shipped
code returns 40.0.

No measurement of inverter B appears anywhere. It does not physically exist.
Every second-pack and fourth-pack figure added here is SIMULATED and labelled at
its definition; only inverter A's 10 % is read off hardware. No hardware was
touched.

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

goodwe_controller/DECISIONS/SAFETY-32-per-pack-bms-floor.md

@@ -81,6 +81,116 @@ grading each pack separately would be. The converse is not true and is not
 claimed — a site can be refused while every pack individually has headroom, which
 costs a shave.
 
+### 3a. ⚠️ FIX ROUND — the reduction was written and argued, and NOT GRADED
+
+PR #48 was rejected because the argument in §4 below justified *writing* the
+reduction and was then not carried into a check. Neither of the two mutations
+below appears anywhere in §6's twelve-row battery: it graded *"the reduction
+dropped"* and *"the bare option handed over"*, and never asked what happens when
+the reduction is the **wrong one**, or when the roster handed to it is
+**sliced**. Both were applied to `app/` by the reviewer and **all 19 files
+stayed green**:
+
+| mutation | Δ | why it survived |
+|---|---|---|
+| `binding_soc_floor()`: `max(floors)` → `min(floors)` | **0 bytes** | every roster in the suite was rule-8-valid or one pack long, so `floors` held **identical numbers** and `max`/`min`/first/last were four spellings of one answer |
+| the `decide()` call site: `self.packs` → `self.packs[:1]` | **+4 bytes** | part 12g asserted `"self.packs" in <the unparsed expression>` — and `self.packs[:1]` **contains that substring** |
+
+The zero-byte one was proved to have actually run rather than assumed:
+`dis.get_instructions` showed the `LOAD_GLOBAL`s as `[float, pack_floor_pct,
+any, min]`, and `binding_soc_floor([Pack("a",50,10), Pack("b",50,35)], 20.0)`
+returned `20.0` where the shipped code returns `35.0`.
+
+**The common cause is this repository's recurring defect** — a check whose DATA
+cannot reach the failure it names. The one check that used a cut-out **above**
+the EMS floor (12c's `_n1_deep`) ran on a roster of **ONE**, where every possible
+reduction agrees. So no check in the suite ever evaluated
+`binding_soc_floor()` on two packs whose floors **differ**.
+
+**And the rule-8 degeneracy is not a defence, by §4's own words.** If
+"unreachable is a claim about today's rule ordering, not a property of this
+function, and `validate_startup_config()` is also `sim/inject.py`'s entry point"
+is enough to *write* the reduction, it is enough to *grade* it. Through
+`sim/inject.py`, which does not run rule 8 at all, `min(floors)` lets the guard
+command a forced discharge to 20 % on a pack whose BMS cuts out at 35 %.
+
+**What was added — no shipped behaviour changed, only what observes it:**
+
+* **`test_peakguard.py` part 12c2** evaluates `binding_soc_floor()` on a roster
+  whose per-pack floors **all differ**. Four **simulated** cut-outs —
+  `30, 25, 40, 35` %, every one strictly above `peak_soc_floor: 20`, so
+  `pack_floor_pct()` selects the cut-out for each and `floors` *is* that tuple in
+  that order. The four candidate reductions are then four different numbers:
+
+      max   = 40   <- the shipped answer
+      min   = 25
+      first = 30   <- "grade the site against pack A", inside the function
+      last  = 35
+      mean  = 32.5
+
+  The extremes sit at **interior** roster positions (index 2 is the max, index 1
+  the min). A two-pack roster structurally cannot separate these — there `max`
+  and `last` coincide and so do `min` and `first` — and neither can three. Four
+  is the smallest roster that separates all four. The precondition is its own
+  check (habit 1), one pack is then raised past the old maximum (habit 7: the
+  **last** pack, which was neither extreme, so the line can only move if the
+  reduction read it), and `peak_soc_floor` is lifted above every cut-out to grade
+  the other side of the conjunction.
+
+* **Part 12g is behaviour now, not source text** (MUTATION.md habit 4). Real
+  `Controller.cycle()`s on a two-pack roster, both packs held at the same SoC and
+  everything else identical, with the packs' own cut-outs as the only thing
+  varied:
+
+      cut-outs A 10 / B 18 % -> decide() got soc_floor=20 %, floor_limited=False
+      cut-outs A 10 / B 35 % -> decide() got soc_floor=35 %, floor_limited=True
+
+  The observable is `PeakDecision.soc_floor` — the argument, echoed back by the
+  shipped `decide()` — so the whole path from `Controller.inverters` to the
+  guard's argument is under test, and the site's **verdict flips** as well as the
+  number. `self.packs[:1]` answers 20 % both times. **Which** option key the floor
+  comes from stays pinned on the source in part 4, because that claim genuinely
+  is about the code's shape; that the option still governs is now graded
+  behaviourally too.
+
+* ⚠️ **A THIRD SURVIVOR, FOUND WHILE FIXING THE FIRST TWO, AND RECORDED RATHER
+  THAN QUIETLY REPAIRED.** The first cut of part 12g varied only **pack B's**
+  cut-out — so `self.packs[-1:]`, grade the site against the **last** pack,
+  agreed with the full roster on both runs and stayed green across all 19 files
+  (+5 bytes). A two-run fixture that only ever moves the second pack pins `[:1]`
+  and not `[-1:]`; it is the same defect one step along, and it was in the fix
+  for this defect. Part 12g now runs the **same pair of cut-outs in both
+  orders**:
+
+      cut-outs A 10 / B 18 % -> soc_floor=20 %, floor_limited=False
+      cut-outs A 10 / B 35 % -> soc_floor=35 %, floor_limited=True
+      ...the SAME PAIR SWAPPED, A 35 / B 18 % -> soc_floor=35 %, floor_limited=True
+
+  `[:1]` answers 20 % on the second run, `[-1:]` answers 20 % on the third, and
+  the roster answers 35 % on both. No single-position slice passes all three.
+  This is the mirror `12h` already ran on the SoC axis, which is where the shape
+  was borrowed from.
+
+* ⚠️ **AND A FOURTH, from the same battery: the EMPTY-roster branch.** Rewriting
+  `binding_soc_floor([])`'s `float(soc_floor)` to `return None` (−43 bytes) was
+  green across all 19 files. It is defensive code — `Controller.inverters` is
+  never empty on a started controller, and `inputs_ok` refuses the cycle before
+  the guard is reached if it were — so nothing in the suite went near it. It is
+  **pinned rather than argued**, in both directions (the option when there is
+  one, `None` when there is not), because a branch with no check is a branch
+  that can be rewritten under a green suite. The check also records why it
+  cannot permit anything either way: `pack_floor_soc` is `None` at an empty
+  roster, and `discharge_permitted()` refuses on a `None` SoC whatever the floor
+  is.
+
+* **`wired_over_limit()` gained a `prepare(ctl)` hook**, inside its retry loop so
+  every attempt grades the same site, which is the only window in which a second
+  inverter can join the roster before the telegrams are fed.
+
+* **In-process mutation rows 22, 22b and 23** record all four survivors, so a
+  later edit that re-degenerates any of these fixtures goes red on a row rather
+  than on nothing.
+
 ## 4. ⚠️ THE HONEST LIMITATION, and it is the reason this record exists
 
 **Under any configuration rule 8 accepts, `binding_soc_floor()` answers