SAFETY-30: pin WHICH thresholds each sign detector is armed with, not just what the numbers are

REVIEW FOUND A MUTATION SURVIVOR THAT UNDOES THE WHOLE PRODUCT OF AC 5, and it
is a coverage defect rather than a behaviour one - the shipped code arms the
detectors correctly today. In `_arm_sign_watchdogs()`, collapsing

    inv.sign_wd.arm(self.sign_cfg if one else self.unit_sign_cfg, ...)

to `arm(self.sign_cfg, ...)` throws the re-derived 250 W / 85 s per-unit pair
away and arms every unit with SAFETY-02's meter-facing 300 W / 180 s - and left
ALL 19 FILES GREEN. Reproduced here before fixing anything: fresh per-mutation
tree, no __pycache__, mounted :ro, graded through tools/mutation_run.sh; -31 B;
19 pass, 0 fail.

WHY NOTHING CAUGHT IT. `grep -rn "sign_wd.cfg" test_*.py` found exactly ONE
threshold assertion, part 7's N=1 arm at (300.0, 1.0) - which the mutation
PRESERVES. Nothing at a roster of two read `inv.sign_wd.cfg` at all. The ledger
mutates the VALUES in SIGN_OPTION_DEFAULTS (M10 250->300, M11 325->180, both
correctly red through the config pins) and never the WIRING that delivers them.
Part 3's behavioural checks cannot close the gap either, and the comment now
says why: B is reversed at ~2000 W with short holds, so it trips under EITHER
pair, and a fault big enough and long enough to trip under both thresholds is
evidence about neither.

THE FIX - test_watchdog.py part 3, on the real two-inverter Controller. Every
`inv.sign_wd.cfg` equals the per-unit pair, `site_sign_wd.cfg` equals the site
pair, and each detector's `against` is its own instrument. Graded against
LITERALS, because `== self.unit_sign_cfg` cannot tell "the per-unit pair" from
"whatever this Controller was handed". Both pairs are printed.

⚠️ AND THE FIXTURE HAD TO CHANGE FOR THE PIN TO MEAN ANYTHING - the recursion
worth naming, because it is the same defect class as the one being closed.
`_sign_site` set `sign_disagree_s`, `unit_sign_disagree_s` AND
`site_sign_disagree_s` all to 1 s, with two of the three magnitude gates at
300 W. A bare equality there discriminates on `min_w` alone: a mis-wiring that
delivered the right magnitude with the WRONG HOLD compares EQUAL to the pair it
was supposed to have. A check comparing two things that happen to be equal
cannot see the difference it names (MUTATION.md's third failure mode). The
three pairs are now pairwise distinct IN BOTH COORDINATES - 250 W / 1 s per
unit, 320 W / 2 s site, 300 W / 3 s shipped - a PRECONDITION asserts that
distinctness so a later edit collapsing them goes red rather than quietly
vacuous, and a second PRECONDITION asserts the literals are the pairs this
Controller actually holds.

VERIFIED BY BREAKING IT. Three mutations, each on its own freshly copied tree
with no __pycache__, mounted :ro, through tools/mutation_run.sh:

  M14  arm() handed self.sign_cfg at every roster        -31 B  RED (was the
       survivor; the AC 5 WIRING check names the wiring)
  M15  right min_w, SHIPPED hold - hold-only mis-wire    +78 B  RED, same pin
  M16  right min_w, SITE hold - hold-only, and it still
       trips inside the drive                            +83 B  RED, and the
       ONLY red in test_watchdog.py

M16 is the one that says the hold half of the equality bites on its own.
Unmutated tree: 19 pass, 0 fail, purged and fingerprinted.

Ledger rows M14-M16 and the write-up in DECISIONS/SAFETY-30-per-unit-sign.md
section 5; a CHANGELOG bullet.

NOT IN THIS PR, so it gets a card rather than a quiet fix: a stuck per-unit
power sensor would false-trip the new per-unit check at N>=2. Already-merged
SAFETY-31 has the identical exposure on the same fixture. Pre-existing N>=2
class, unreachable at the deployed roster of one.

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

goodwe_controller/DECISIONS/SAFETY-30-per-unit-sign.md

@@ -377,6 +377,9 @@ size-preserving edit is what TEST-15 turned into a false survivor once already.
 | M11 | `watchdog.py` | `site_sign_disagree_s` 325 → 180, i.e. **the number carried** | **+0 B** | **RED** — the measured-215 s check and the CFG-03 pin |
 | M12 | `arbiter.py` | `sign_site` scoped `SCOPE_UNIT` | **+0 B** | **RED** — `test_arbiter.py` **and** `test_peakguard.py` |
 | M13 | `validate.py` | the `unit_sign_disagree_w` rule removed | −126 B | **RED** — `test_validate.py` |
+| **M14** | `main.py` | **`arm()` handed `self.sign_cfg` at EVERY roster** — the WIRING, not the values | −31 B | **SURVIVOR at review — GAP CLOSED**, then RED. See below |
+| M15 | `main.py` | per-unit `arm()` given the right `min_w` and the SHIPPED hold — a HOLD-ONLY mis-wire | +78 B | **RED** — the same wiring pin |
+| M16 | `main.py` | per-unit `arm()` given the right `min_w` and the SITE hold — hold-only again, and behaviour-preserving | +83 B | **RED** — the wiring pin, and the ONLY red in `test_watchdog.py` |
 
 ### M4 is recorded as a survivor because it was one
 
@@ -400,6 +403,57 @@ cycles, zero calls, printed. A counter can only be zero for one reason. The
 mutation was re-run against it and is red; the run that found it was discarded
 along with its tree, so this is a result and not an artefact.
 
+### M14: the VALUES were pinned and the WIRING was not
+
+M10 and M11 mutate the numbers in `watchdog.SIGN_OPTION_DEFAULTS` and both are
+red through the config pins. Neither of them touches the line that DELIVERS
+those numbers to a detector:
+
+```python
+inv.sign_wd.arm(self.sign_cfg if one else self.unit_sign_cfg,
+                AGAINST_METER if one else AGAINST_OWN_POWER)
+```
+
+Drop the conditional — `arm(self.sign_cfg, ...)` — and every unit is armed with
+SAFETY-02's meter-facing pair instead of the re-derived per-unit one. At review
+that left **all 19 files green**. `grep -rn "sign_wd.cfg" test_*.py` found
+exactly one threshold assertion, and it is §7's N=1 arm — `(300.0, 1.0)` —
+which the mutation PRESERVES. Nothing anywhere read `inv.sign_wd.cfg` at a
+roster of two.
+
+The behavioural checks in part 3 cannot close it and it is worth saying why: B
+is reversed at ~2000 W and every hold in that fixture is short, so B trips under
+either pair. **A fault big enough and long enough to trip under both thresholds
+is evidence about neither.**
+
+What the survivor costs in the field is the whole product of §3: at
+`config.yaml`'s own defaults the per-unit check would run at `sign_disagree_s`
+**180 s instead of 85 s** — 2.1× slower to park a reversed inverter — and its
+gate would move from 250 W to 300 W, so a unit reversing a share between the two
+becomes invisible, while `SIGN_OPTION_DEFAULTS`, `config.yaml` and §3 all go on
+describing a pair the running code does not use. With CI green.
+
+**Closed by a wiring pin in `test_watchdog.py` part 3**, on the real
+two-inverter Controller: every `inv.sign_wd.cfg` equals the per-unit pair,
+`site_sign_wd.cfg` equals the site pair, and each detector's `against` is its
+own instrument — all graded **against literals**, since `== self.unit_sign_cfg`
+cannot tell *the per-unit pair* from *whatever this Controller was handed*.
+
+⚠️ **And the fixture had to be changed for that pin to mean anything.**
+`_sign_site` set `unit_sign_disagree_s: 1` **and** `site_sign_disagree_s: 1`
+**and** `sign_disagree_s: 1`, with two of the three magnitude gates at 300 W. A
+bare equality there discriminates on `min_w` alone: a mis-wiring that delivered
+the right magnitude with the wrong hold would compare EQUAL to the pair it was
+supposed to have. That is this document's own §5 lesson and MUTATION.md's third
+failure mode — a check comparing two things that happen to be equal cannot see
+the difference it names — reappearing inside the fix for it. The three pairs are
+now pairwise distinct **in both coordinates** (250 W / 1 s, 320 W / 2 s,
+300 W / 3 s), a PRECONDITION check asserts that distinctness so a later edit
+collapsing them goes red rather than quietly vacuous, and both pairs are
+**printed**. M15 and M16 exist to show the hold half actually bites: right
+magnitude, wrong hold, red both times — and M16, whose wrong hold still trips
+inside the drive, is red on the wiring pin and on **nothing else** in that file.
+
 ## 6. What this card does NOT close
 
 * **The flapping-load blind spot in the SITE comparison.** §3, at length. Present