fix(ci): stop treating markdown as frontend evidence-bearing code (#16693)

Co-authored-by: vasco <vasco.schiavo@protonmail.com>

.github/scripts/check_pr_description.py

@@ -57,6 +57,8 @@ FRONTEND_FILE_EXTENSIONS: tuple[str, ...] = (
     ".sass",
     ".less",
 )
+# Docs carry no visual state, so a screenshot can't evidence a change to them.
+DOCUMENTATION_FILE_EXTENSIONS: tuple[str, ...] = (".md", ".mdx")
 FRONTEND_CONFIG_GLOBS: tuple[str, ...] = (
     "tailwind.config.*",
     "vite.config.*",
@@ -155,9 +157,11 @@ def extract_human_note(body: str) -> str:
 def is_frontend_file(path: str) -> bool:
     """Return True if a changed file should be treated as frontend code."""
     normalized = path.lstrip("./")
+    lower = normalized.lower()
+    if lower.endswith(DOCUMENTATION_FILE_EXTENSIONS):
+        return False
     if any(normalized.startswith(prefix) for prefix in FRONTEND_PATH_PREFIXES):
         return True
-    lower = normalized.lower()
     if any(lower.endswith(ext) for ext in FRONTEND_FILE_EXTENSIONS):
         return True
     name = normalized.split("/")[-1]

.github/scripts/tests/test_pr_description.py

@@ -8,6 +8,8 @@ from unittest.mock import patch
 sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
 
 from check_pr_description import (
+    is_frontend_file,
+    touches_frontend,
     extract_linked_issue_numbers,
     extract_pr_type,
     validate_linked_issue_ready,
@@ -222,3 +224,23 @@ https://youtube.com/watch?v=abc123
 """
     errors = validate_bug_fix_evidence(body)
     assert errors == []
+
+
+def test_markdown_under_frontend_prefix_is_not_frontend():
+    assert not is_frontend_file("__tests__/router.md")
+    assert not is_frontend_file("src/notes.md")
+    assert not is_frontend_file("public/README.mdx")
+
+def test_markdown_outside_frontend_prefix_still_not_frontend():
+    assert not is_frontend_file("docs/README.md")
+
+def test_frontend_code_under_prefix_still_frontend():
+    assert is_frontend_file("src/app.tsx")
+    assert is_frontend_file("__tests__/routes/launch.test.tsx")
+    assert is_frontend_file("src/styles/main.css")
+
+def test_docs_only_change_does_not_require_frontend_evidence():
+    assert not touches_frontend(["__tests__/router.md", "docs/README.md"])
+
+def test_mixed_change_still_requires_frontend_evidence():
+    assert touches_frontend(["__tests__/router.md", "src/app.tsx"])