fix: restore render_readme; the hacs check fails because the repo is private

Corrects the previous commit, which removed `render_readme` from
hacs.json on a wrong diagnosis. Two errors there:

1. `render_readme` IS in HACS_MANIFEST_JSON_SCHEMA
   (custom_components/hacs/utils/validate.py), so it was never the
   schema violation I claimed, and HacsManifest defaults it to False --
   dropping it would have silently stopped HACS rendering the README on
   the integration's HACS page. Restored.

2. The real cause of both remaining failures is that this repository is
   **private**. hacsjson's error text ("has an invalid 'hacs.json'
   file") is raised on `rawhacsjson is None`, not on a schema error --
   a schema error would surface as a humanized voluptuous message.
   get_hacs_json_raw() fetches
   raw.githubusercontent.com/<repo>/<ref>/hacs.json *unauthenticated*
   (wrapped in @return_none_on_exception), and that 404s for a private
   repo. get_integration_manifest() fetches manifest.json the same way,
   which is why integration_manifest reports "expected a dictionary.
   Got None" -- voluptuous validating None, not a bad manifest. Both
   files are in fact valid and manifest.json already carries all six
   keys INTEGRATION_MANIFEST_JSON_SCHEMA requires.

So these last 2/9 checks cannot pass while the repo is private, and no
repo-side change can fix them; they should clear on their own when it
goes public. The other four failures the previous commit addressed
(topics, description, information, brands) did clear -- confirmed in
run 35296482777, which went 6/9 failed -> 2/9 failed.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NxJYWgGJtCw13qUHZtG8ki

hacs.json

@@ -1,5 +1,6 @@
 {
   "name": "OpenAI Compatible",
   "content_in_root": false,
-  "homeassistant": "2026.9.0"
+  "homeassistant": "2026.9.0",
+  "render_readme": true
 }