feat: run standard-files test via browser-based plugin

Route test id 9 (standard files: robots.txt, sitemap.xml, RSS/Atom feed,
security.txt) through the sitespeed.io plugin plugin-standard-files instead
of the requests-based Python implementation:

- test_helper: move TEST_STANDARD_FILES into TEST_USE_SITESPEED (run via the
  shared sitespeed pass + plugin-webperf-core aggregation), dummy in
  TEST_ALL_FUNCS, drop from the TOMORROW roadmap.
- standard_files.py: replace the 600-line requests-based checks with a thin
  shim that runs sitespeed with the plugin and reads the standard-files
  issues out of webperf-core.json (kept as a standalone, requests-free
  fallback for test id 9).
- package.json: add plugin-standard-files 2026.6.2 (plugin-webperf-core is
  already 2026.6.1 on main, which aggregates the plugin's summary).
- CREDITS: attribute plugin-standard-files.

Fetching these files via real headless Chrome uses a genuine browser TLS
fingerprint, so enterprise WAFs (Akamai, Imperva, F5) no longer drop the
connection the way they blocked python-requests. This is what made the old
test return empty results on sites like bolagsverket.se.

Closes #1470

Author: marcusosterberg

CREDITS.md

@@ -46,6 +46,9 @@ License: MIT
 ### [plugin-pagenotfound](https://www.npmjs.com/package/plugin-pagenotfound)
 License: MIT
 
+### [plugin-standard-files](https://www.npmjs.com/package/plugin-standard-files)
+License: MIT
+
 ### [plugin-accessibility-statement](https://www.npmjs.com/package/plugin-accessibility-statement)
 License: MIT
 

helpers/test_helper.py

@@ -48,7 +48,7 @@ def run_dummy_test(global_translation, url):
 TEST_ALL_FUNCS = {
         TEST_PAGE_NOT_FOUND: run_dummy_test,
         TEST_WEBBKOLL: run_test_privacy_webbkollen,
-        TEST_STANDARD_FILES:run_test_standard_files,
+        TEST_STANDARD_FILES: run_dummy_test,
         TEST_SITESPEED: run_test_performance_sitespeed_io,
         TEST_PA11Y: run_test_a11y_pa11y,
         TEST_HTTP: run_test_http_validator,
@@ -78,6 +78,7 @@ def run_dummy_test(global_translation, url):
 
 TEST_USE_SITESPEED = {
         TEST_PAGE_NOT_FOUND: 'plugin-pagenotfound',
+        TEST_STANDARD_FILES: 'plugin-standard-files',
         TEST_A11Y_STATEMENT: 'plugin-accessibility-statement',
         TEST_LINT_CSS: 'plugin-css',
         TEST_LINT_HTML: 'plugin-html',
@@ -86,7 +87,6 @@ def run_dummy_test(global_translation, url):
     }
 
 TEST_USE_SITESPEED_TOMORROW = {
-        TEST_STANDARD_FILES:run_test_standard_files,
         TEST_SITESPEED: run_test_performance_sitespeed_io,
         TEST_HTTP: run_test_http_validator,
         TEST_ENERGY_EFFICIENCY: run_test_energy_efficiency,

package.json

@@ -23,6 +23,7 @@
     "plugin-html": "2026.6.0",
     "plugin-javascript": "2026.6.0",
     "plugin-pagenotfound": "2026.6.0",
+    "plugin-standard-files": "2026.6.2",
     "plugin-accessibility-statement": "2026.6.0",
     "plugin-webperf-core": "2026.6.1"
   },