wip: 891 round 14 — scope the disarm advice, drop a rottable duplicate

docs/guard-inventory.md

@@ -462,7 +462,7 @@ Read the artifacts instead. The row's `Proof ref` and `scripts/tests/mutation_ma
 against each other and EXECUTED by `test_mutation_harness.py`, so a stale ref there is a red rather
 than a reading error. The arms are explained in `scripts/tests/test_hook_fire_log.py` itself, in the
 comments through `instrumentation_faults`; the list partway down that function enumerates the arms
-byte-identity does NOT subsume, and every one of those is pinned by its own test.
+byte-identity does NOT subsume.
 
 One thing no artifact records, so it is written here: **the `Blocks` column is not machine-checked at
 all.** `inventory_rows()` parses that cell into a discard variable and nothing else reads it, so a

scripts/tests/test_hook_fire_log.py

@@ -177,9 +177,10 @@ def instrumentation_faults(text: str, name: str) -> list[str]:
     # believed: PRESENCE and the no-mode-token arm were unsubsumed AND unpinned, because
     # `…_LOSES_its_instrumentation_…` looks like their proof and is not (it asserts only that the
     # fault list is NON-EMPTY, and a stripped hook trips four arms, so removing one leaves three
-    # answering). Disarm an arm here with `pass`, never `if False:` — several fall through to a
-    # `.group(1)` on None and red with an AttributeError, a red for the wrong reason that reads like
-    # a proof and cost this branch two review rounds. A
+    # answering). Disarm an arm here with `pass`. `if False:` is safe on an arm with no `elif` after
+    # it — `mutation_manifest.py` disarms byte-identity that way every run — but on the two begin-call
+    # arms below it falls through to a `.group(1)` on None and reds with an AttributeError: a red for
+    # the wrong reason that reads like a proof, and cost this branch two review rounds. A
     # hook carrying both canonical lines plus `ETV_HOOK_FIRE_DISABLE=1` trips exactly one fault, and
     # it is not byte-identity's, so a reader who sorts those into "already covered" deletes a live
     # detector.