fix: correct verify-build diagnostics and close two robustness gaps (closes #180)

The both-markers diagnostic claimed the debug branch was still live. It is
not: with the __BUILD_DEBUG__ define removed, the emitted bundle carries
`typeof __BUILD_DEBUG__<"u"?__BUILD_DEBUG__:!1`, and in extension context the
identifier is undeclared, so DEBUG evaluates to false at runtime. The message
now states what the check does prove -- DEBUG was not resolved at build time,
so the release/debug distinction is no longer enforced and which way the
unresolved fallback evaluates is an accident a refactor can flip -- and it
remains a hard failure. The other seven failure messages were reviewed and
none needed rewording.

has_marker no longer swallows grep's exit 2 with 2>/dev/null. Match and
no-match are answers about the emitted output; an unreadable file is not, and
is now reported as a permissions or I/O fault instead of as "the emitted
output changed shape". Both paths still fail hard.

The unlisted-bundle scan no longer filters by extension, so the endsWith(".js")
test in build.js is the only place that assumption lives. A bundle emitted
under another extension previously escaped the manifest and the cross-check at
once; it now fails as unlisted. Both sites carry a comment naming the other.

Also: the manifest must be readable and a listed bundle must be non-empty,
so a vacuous input fails loudly rather than reaching a marker check that
cannot prove anything.

TODO.md

@@ -44,6 +44,11 @@ undefined identifiers, which is how
 
 # Completed Steps
 
+- 2026-08-11: `script/verify-build` diagnostics corrected: the both-markers
+  message now states what is and is not proven, an unreadable bundle is
+  diagnosed as an I/O fault rather than as changed output, and the `*.js`
+  assumption lives only in `build.js`
+  ([#180](https://git.eeqj.de/sneak/AutistMask/issues/180)).
 - 2026-08-11: `TODO.md` Workflow rewritten to the branch-and-PR-per-issue model
   on `next`, with Status and Next Step refreshed
   ([#191](https://git.eeqj.de/sneak/AutistMask/issues/191)).

build.js

@@ -29,6 +29,11 @@ function repoRelative(p) {
 // reports every input that contributed to an output in the metafile, which is
 // the authoritative answer to "is constants.js in this bundle" — unlike
 // searching the minified text, it does not depend on what survived minification.
+//
+// The ".js" filter below is the only place that assumption lives:
+// script/verify-build searches every file under dist/ for a marker, without
+// filtering by extension, so a bundle emitted under some other extension fails
+// there as unlisted rather than escaping both checks at once.
 function outputsContainingAuditedModule(metafile) {
     return Object.entries(metafile.outputs)
         .filter(([outFile, info]) => {

script/verify-build

@@ -34,16 +34,31 @@ fail() {
     exit 1
 }
 
+# Is the literal $1 present in the file $2? Match (grep exit 0) and no-match
+# (exit 1) are answers about the emitted output. Anything else (exit 2: the
+# file could not be read) is not an answer at all, and must not be reported as
+# "no marker" — that would blame the bundle for a permissions or I/O fault.
 has_marker() {
-    grep -q -F "$1" "$2" 2>/dev/null
+    _hm_status=0
+    grep -q -F -e "$1" -- "$2" || _hm_status=$?
+    case "$_hm_status" in
+    0) return 0 ;;
+    1) return 1 ;;
+    *)
+        fail "grep exited $_hm_status reading $2, so the file could not be
+    searched and its DEBUG state was not checked at all. That is a permissions
+    or I/O fault on the artifact, not a change in the emitted output. Refusing
+    to report success."
+        ;;
+    esac
 }
 
 # Read one bundle's DEBUG state into MARKER. Exactly one marker must be
 # present. Both means the ternary in constants.js was never folded, which is
 # what happens when the __BUILD_DEBUG__ define goes missing from build.js:
-# DEBUG stops being known at build time and the debug branch is live again.
+# DEBUG stops being known at build time. Neither means we are reading output
-# Neither means we are reading output we do not understand. Both are hard
+# we do not understand. Both are hard failures; neither is ever treated as
-# failures; neither is ever treated as absence of a problem.
+# absence of a problem.
 read_marker() {
     _file="$1"
     _on=no
@@ -52,9 +67,14 @@ read_marker() {
     if has_marker "$MARKER_OFF" "$_file"; then _off=yes; fi
 
     if [ "$_on" = yes ] && [ "$_off" = yes ]; then
-        fail "$_file carries both debug markers, so the build-time DEBUG value
+        fail "$_file carries both debug markers, so DEBUG was not resolved at
-    was never resolved and the debug branch is still live. Check that build.js
+    build time: the ternary in src/shared/constants.js survived into the
-    still defines __BUILD_DEBUG__."
+    emitted output. This does not mean the debug branch is live in this
+    artifact: an unresolved __BUILD_DEBUG__ is undeclared in extension
+    context, so DEBUG evaluates to false at runtime. It does mean the
+    release/debug distinction is no longer enforced at build time, and which
+    way that fallback happens to evaluate is then an accident a refactor can
+    flip. Check that build.js still defines __BUILD_DEBUG__."
     fi
     if [ "$_on" = no ] && [ "$_off" = no ]; then
         fail "$_file carries no debug marker, so its DEBUG state cannot be
@@ -70,13 +90,20 @@ read_marker() {
 }
 
 # The manifest says which bundles must carry a marker. This says no other
-# emitted bundle may carry one, which catches a manifest that has gone stale
+# emitted file may carry one, which catches a manifest that has gone stale
 # or short rather than trusting whatever it happens to list.
+#
+# Deliberately unfiltered by extension. build.js selects manifest entries with
+# an endsWith(".js") test; repeating that literal here would mean a bundle
+# emitted under some other extension escaped the manifest AND this check at
+# once, which is the correlated blind spot the two-source design exists to
+# avoid. Every file under dist/ is searched, so build.js's filter is the only
+# place the assumption lives and this check is what catches it being wrong.
 check_unlisted_bundles() {
-    _listing="$(find dist -type f -name '*.js' | sort)"
+    _listing="$(find dist -type f | sort)"
     while read -r _file; do
         [ -n "$_file" ] || continue
-        if grep -q -x -F "$_file" "$MANIFEST"; then
+        if grep -q -x -F -e "$_file" -- "$MANIFEST"; then
             continue
         fi
         if has_marker "$MARKER_ON" "$_file" ||
@@ -113,12 +140,18 @@ main() {
         fail "$MANIFEST is empty, so no emitted bundle was found to contain
     src/shared/constants.js. That is never correct, so it is a failure and not
     a pass."
+    [ -r "$MANIFEST" ] ||
+        fail "$MANIFEST is not readable, so nothing was inspected. That is a
+    permissions or I/O fault, not a pass."
 
     count=0
     while read -r file; do
         [ -n "$file" ] || continue
         [ -f "$file" ] ||
             fail "$MANIFEST lists $file, which does not exist."
+        [ -s "$file" ] ||
+            fail "$MANIFEST lists $file, which is empty. An empty bundle
+    carries no marker and proves nothing, so this is a failure and not a pass."
         read_marker "$file"
         [ "$MARKER" = "$expected" ] ||
             fail "$file is $MARKER but this build expects $expected."