ci: check_runner_labels.sh ignores a trailing comment on runs-on (Refs #6433)

Makefile

@@ -255,6 +255,7 @@ tier3:
 	@echo "Checking build.rs crate-root escapes (v0.31.1 yank class)..."
 	@bash scripts/check_build_rs_paths.sh
 	@echo "Checking self-hosted CI jobs pin a discriminating runner label..."
+	@bash scripts/check_runner_labels.sh --self-test
 	@bash scripts/check_runner_labels.sh
 	@echo "Checking the toolchain-ceiling guard's comparator (aprender#2370)..."
 	@bash scripts/check_clippy_current_stable.sh --self-test

docs/roadmaps/entries/PMAT-6433.yaml

@@ -0,0 +1,20 @@
+- id: PMAT-6433
+  github_issue: 6433
+  item_type: task
+  title: 'check_runner_labels.sh judges the runs-on value, not its trailing comment'
+  status: in_progress
+  priority: medium
+  assigned_to: aprender-wsweep
+  created: 2026-10-27T06:20:00Z
+  updated: 2026-10-27T06:20:00Z
+  spec: null
+  acceptance_criteria:
+  - 'a runs-on line whose only discriminating label is inside a trailing # comment fails check_runner_labels.sh'
+  - 'check_runner_labels.sh --self-test has must-fail rows for comment-only labels, and make runs it'
+  phases: []
+  subtasks: []
+  estimated_effort: null
+  labels:
+  - kind:code
+  notes: null
+  epic: 4741

docs/roadmaps/roadmap.yaml

@@ -26535,3 +26535,23 @@ Not done, pending the ruling: moving the 31 fixture files to an obviously synthe
   - kind:code
   notes: null
   epic: 6390
+- id: PMAT-6433
+  github_issue: 6433
+  item_type: task
+  title: 'check_runner_labels.sh judges the runs-on value, not its trailing comment'
+  status: in_progress
+  priority: medium
+  assigned_to: aprender-wsweep
+  created: 2026-10-27T06:20:00Z
+  updated: 2026-10-27T06:20:00Z
+  spec: null
+  acceptance_criteria:
+  - 'a runs-on line whose only discriminating label is inside a trailing # comment fails check_runner_labels.sh'
+  - 'check_runner_labels.sh --self-test has must-fail rows for comment-only labels, and make runs it'
+  phases: []
+  subtasks: []
+  estimated_effort: null
+  labels:
+  - kind:code
+  notes: null
+  epic: 4741

scripts/check_runner_labels.sh

@@ -28,10 +28,34 @@ cd "$(dirname "$0")/.."
 DISCRIM='clean-room|cuda|gpu|rtx4090|ada|blackwell|gb10|apple-silicon|m4|perf-solo|mini-builder|review-light|kfocus'
 fail=0
 
+# A selector is judged on its YAML value only: a trailing `# comment` must not
+# supply the label (#6433: `[self-hosted, X64, Linux, intel]  # perf-solo` passed).
+pinned() { # $1 = text after `runs-on:`; true when it carries a discriminating label
+  local sel=${1%%#*}
+  grep -qE "$DISCRIM" <<< "$sel"
+}
+
+if [ "${1:-}" = "--self-test" ]; then
+  bad=0
+  expect() { # $1 = want (ok|bad), $2 = selector line
+    local got=bad
+    if pinned "$2"; then got=ok; fi
+    if [ "$got" != "$1" ]; then echo "FAIL self-test: want $1, got $got: $2" >&2; bad=1; fi
+  }
+  expect ok  '[self-hosted, Linux, X64, clean-room]'
+  expect ok  '[self-hosted, X64, Linux, intel, perf-solo]  # one box'
+  expect bad '[self-hosted, X64, Linux]'
+  expect bad '[self-hosted, X64, Linux, intel]  # perf-solo'
+  expect bad '[self-hosted, X64, Linux]  # clean-room'
+  [ "$bad" -eq 0 ] || exit 1
+  echo "✓ check_runner_labels --self-test: 5 rows (2 pass, 3 must-fail incl. comment-only labels)"
+  exit 0
+fi
+
 while IFS=: read -r file line sel; do
   # Only inline self-hosted selectors.
   grep -q 'self-hosted' <<< "$sel" || continue
-  if ! grep -qE "$DISCRIM" <<< "$sel" ; then
+  if ! pinned "$sel"; then
     echo "::error file=${file},line=${line}::self-hosted job lacks a discriminating runner label (need clean-room or a GPU/macOS label): ${sel# }"
     fail=1
   fi