docs: reconcile the ADRs, gates and audit log with the shipped behaviour

Why

A six-agent review of the two preceding commits found their code sound -- the
differential claim holds, the published hook contract is byte-unchanged -- but
their prose drifted from it in three ways: statements of fact the code
contradicts, markers in a convention this repo does not use, and figures that
went stale when the merge changed what they counted.

Implementation Notes

ADR-0025's edge-path table is rewritten around one stated doctrine: exit 0 is
audited and clean, exit 1 is audited with findings or a target present but
unreadable, exit 2 is that nothing was audited. Its old row 1 promised "one
generic matches-neither message" for three different inputs; there are three
distinct messages, and the missing-path case exited 1 until the preceding commit
fixed it. Rows are added for the preflight and CDPATH changes, because a table
claiming to enumerate every entry-point behaviour change reproduces its own
"an earlier revision of this ADR said they were behaviour-neutral" failure if it
omits any.

ADR-0025 also gains a Consequences supersession record in ADR-0016's form:
partially-superseded entries for 0008, 0014, 0020 and 0021, and explicit
"is not superseded" entries with reasoning for the rest. Twelve ADRs are amended
and it previously listed none.

ADR-0008 moves from an amendment note to partially superseded. Its contract
genuinely narrowed -- an agent .md outside an agents/ directory was audited
before the merge and is refused now -- and ADR-0020 already recorded that the
merge "reopens ADR-0008". Its detector description said "a path under
.apm/agents/", the phrasing ADR-0025 rejects as wider than the script and
circular; the shipped rule is a .md whose immediate parent is named agents/, at
any scope.

ADR-0020's amendment claimed the boundary resolver is sourced by
validate-provenance.sh. It is not, and never was; only validate.sh sources it,
once per mode branch. Three Home-column entries pointed at reference filenames
the merge renamed, one of which now resolves to two files because its row covers
skills and agents.

Five ADRs opened with "Skill renamed per ADR-0025", a form this repo does not
use, in the same commit that used the conventional "Amended by ADR-0025" twice.
They are normalized. "Renamed" was also wrong: the BREAKING-CHANGE trailer says
the skills were removed and their flows merged.

SIMPLIFICATION-AUDIT.md had 2026-09-15 notes attached to headlines that were
never updated, against its own convention of correcting in place with
strikethrough. Every figure here was re-derived at HEAD by command, and several
differed from the review's own numbers, so the notes record the basis rather
than the result alone.

LESSONS.md asserted the two review-time suite failures were the SIGPIPE race.
The commit that fixed that race explicitly declined to claim it -- the suite was
running while agents edited live config files -- so the hedge is restored.

Impact

No code, test or configuration change; documentation only. Suites stay 20/20
strict with 0 skipped and 374/374 bats. No gate parses ADR or gates.md content,
so nothing here is load-bearing for a hook.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YR2CjVumUbEGWcMikcoXBD

LESSONS.md

@@ -136,4 +136,8 @@ A retrofit replaced "keep reference chains one level deep" with "two hops, never
 
 ## 2026-09-15 — A rare flake in a pipefail suite is a race until proven otherwise
 
-The pre-push `run-tests` failed 2 of 3 full runs, on a different suite each time, and neither failure reproduced alone, so it was treated as noise. The cause was `echo "$OUT" | grep -q P` under `set -o pipefail`, at 116 sites. `grep -q` exits on its first match, `echo` takes SIGPIPE on its next write, and pipefail reports correct output as "no match". Unforced it failed about once in 670 runs; with a pause forced before the last line, 50 of 50. Fix: use `grep -q P <<< "$OUT"` (a here-string has no writer process to race), and add a static guard (`tests/test-no-pipefail-early-exit-grep.sh`) instead of relying on convention.
+The pre-push `run-tests` failed 2 of 3 full runs, on a different suite each time, and neither failure reproduced alone, so it was treated as noise. Investigating it found a real race at 116 sites: `echo "$OUT" | grep -q P` under `set -o pipefail`. `grep -q` exits on its first match, `echo` takes SIGPIPE on its next write, and pipefail reports correct output as "no match". Unforced it failed about once in 670 runs; with a pause forced before the last line, 50 of 50. **The two failures that started this were never proven to be that race** — they are consistent with it, but the suite was running while agents edited live config files in place, and a brief change to `.vale.ini` or `.pre-commit-hooks.yaml` produces exactly those two failures. The race is real and is fixed either way; what is not established is that it caused the symptom that led to finding it. Fix: use `grep -q P <<< "$OUT"` (a here-string has no writer process to race), and add a static guard (`tests/test-no-pipefail-early-exit-grep.sh`) instead of relying on convention.
+
+## 2026-09-16 — A static guard covers exactly the spellings its regex models
+
+The guard added above (`tests/test-no-pipefail-early-exit-grep.sh`) reported the tree clean the day it landed, and the tree was not clean. Its pattern could not see a multi-stage pipeline (`echo x | filter | grep -q y`), a pipeline wrapped after a trailing `|`, or `set -o errexit -o pipefail` — the last a file-level miss that silently skipped every site in that file. Five live vulnerable sites sat in `tests/test-apm-current-hook.sh` while the suite reported green, and the fixtures carried 4 of the 12 vulnerable spellings that turned out to exist. A clean verdict from a static scanner is a claim about its regex, not about the tree. Fix: before trusting one, enumerate the spellings of the defect and measure the miss surface against them; and write the scanner's remit and its known false-positive shapes into the gate's own documentation, so the next reader knows what the green covers.