chore(github): ask issue authors without the fix checkbox about a PR (#16271)

* chore(github): ask issue authors without the fix checkbox about a PR

Issues filed through `gh issue create --body` or the API skip the issue
form, so they never carry the "I am working on a fix" checkbox. When the
"Contributing a fix" section is missing from the body, the triage
workflow now comments asking the author whether they plan to open a
pull request. The regression form gets the same checkbox, so its
reports are not asked.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* test(github): cover the issue fix-intent classifier

The classifier moves from the triage workflow into
.github/scripts/issue-fix-intent.sh, with a test that CI runs next to the
other workflow script tests. The workflow checks out the default branch
before the step so the script is available.

A "Contributing a fix" heading without its checkbox now counts as
missing. A hand-written body containing only the heading was classified
as unchecked and got neither an assignment nor the question.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

.github/scripts/issue-fix-intent.sh

@@ -0,0 +1,19 @@
+#!/usr/bin/env bash
+
+# Reads an issue body on stdin and prints whether the author ticked the issue
+# form's "I am working on a fix" checkbox: "checked", "unchecked", or
+# "missing" when the body has no such checkbox, e.g. an issue filed with
+# `gh issue create --body`. Only the checkbox under the form's own
+# "Contributing a fix" heading counts, not the same text in another section.
+
+set -euo pipefail
+
+awk '
+  { sub(/\r$/, "") }
+  /^### / { in_fix = ($0 ~ /^### Contributing a fix[[:space:]]*$/); next }
+  in_fix && /^- \[[ xX]\] I am working on a fix[[:space:]]*$/ {
+    seen = 1
+    if ($0 !~ /^- \[ \]/) checked = 1
+  }
+  END { print checked ? "checked" : seen ? "unchecked" : "missing" }
+'

.github/scripts/issue-fix-intent.test.sh

@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+script_dir=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
+
+assert_intent() {
+  local expected=$1
+  local body=$2
+  local actual
+  actual=$("$script_dir/issue-fix-intent.sh" <<< "$body")
+  if [ "$actual" != "$expected" ]; then
+    printf 'expected %s, got %s for body:\n%s\n' "$expected" "$actual" "$body" >&2
+    exit 1
+  fi
+}
+
+assert_intent checked $'### Describe the Bug\n\nIt breaks.\n\n### Contributing a fix\n\n- [x] I am working on a fix'
+assert_intent checked $'### Contributing a fix\r\n\r\n- [X] I am working on a fix\r'
+assert_intent unchecked $'### Describe the Bug\n\nIt breaks.\n\n### Contributing a fix\n\n- [ ] I am working on a fix'
+assert_intent missing $'### Describe the Bug\n\nIt breaks.\n\nA fix is prepared and will be submitted as a PR shortly.'
+assert_intent missing $'### Describe the Bug\n\n- [x] I am working on a fix'
+assert_intent missing $'### Contributing a fix\n\nI will send a PR.'
+assert_intent missing ''