fix(dataset): serve nested TinyMCE assets so the description editor loads

The description editor (TinyMCE, base_url /dataset/dist) loads its runtime from
nested folders — models/dom/, themes/silver/, skins/, icons/. splent's
BaseBlueprint asset route only matches a single path segment, so every nested
file 404'd and TinyMCE never initialised (no textarea, no editor visible).

Add a dataset-owned route /dataset/dist/<path:filename> (send_from_directory,
binary-safe, longer prefix wins) that serves the whole compiled tree, pinning
.js/.css MIME types. Same fix pattern as the generator Pyodide assets.

Verified: the nested assets now return 200 and Selenium confirms the editor
renders (.tox-tinymce present). Regression tests added.

Author: drorganvidez

app/features/dataset/routes.py

@@ -21,6 +21,7 @@
     render_template,
     request,
     send_file,
+    send_from_directory,
     url_for,
 )
 from flask_login import current_user, login_required
@@ -345,6 +346,32 @@ def new_dataset_version(dataset_id):
     )
 
 
+_DATASET_ASSETS_DIR = os.path.join(os.path.dirname(__file__), "assets")
+
+_ASSET_MIMETYPES = {
+    ".js": "text/javascript",
+    ".mjs": "text/javascript",
+    ".css": "text/css",
+}
+
+
+@dataset_bp.route("/dataset/dist/<path:filename>", methods=["GET"])
+def dist_asset(filename):
+    """Serve the dataset's compiled front-end assets.
+
+    splent's BaseBlueprint asset route only matches a single path segment and
+    reads files in text mode, so it cannot serve the nested TinyMCE runtime
+    (models/, themes/, skins/, icons/, plugins/) the description editor loads
+    from base_url '/dataset/dist'. This route serves that tree with a path
+    converter and binary-safe streaming, taking precedence via its longer prefix.
+    """
+    response = send_from_directory(os.path.join(_DATASET_ASSETS_DIR, "dist"), filename)
+    mimetype = _ASSET_MIMETYPES.get(os.path.splitext(filename)[1])
+    if mimetype:
+        response.headers["Content-Type"] = mimetype
+    return response
+
+
 @dataset_bp.route("/datasets/list", methods=["GET"])
 @login_required
 def list_dataset():

app/features/dataset/tests/test_integration.py

@@ -414,3 +414,20 @@ def test_new_version_validation_error_returns_400(test_client):
         response = test_client.post("/dataset/1/new-version", data={}, content_type="multipart/form-data")
     assert response.status_code == 400
     test_client.get("/logout", follow_redirects=True)
+
+
+# --- Compiled asset serving (nested TinyMCE files) -----------------------
+
+
+def test_dist_asset_serves_nested_tinymce_model(test_client):
+    # splent's BaseBlueprint asset route 404s on nested paths; dist_asset must
+    # serve them so the TinyMCE description editor can load (base_url /dataset/dist).
+    response = test_client.get("/dataset/dist/models/dom/model.js")
+    assert response.status_code == 200
+    assert "javascript" in response.headers["Content-Type"]
+
+
+def test_dist_asset_serves_nested_skin_css(test_client):
+    response = test_client.get("/dataset/dist/skins/ui/oxide/skin.min.css")
+    assert response.status_code == 200
+    assert "text/css" in response.headers["Content-Type"]