Match PyProjectConfig shape for pyproject; add pack_id/module_name/source query filters

Two reviewer-requested improvements to GET /node_startup_errors:

1. Emit the pyproject metadata in the same {project: {...}, tool_comfy: {...}}
   shape that comfy_config.config_parser.extract_node_configuration already
   returns, instead of inventing a flat {pack_id, display_name, ...} bag.
   API consumers can now parse the pyproject block straight through the
   shared PyProjectConfig pydantic model. Empty / default-valued leaves
   are pruned by a small recursive _prune_empty helper so the payload
   stays compact, but nesting and field names match the source-of-truth.

2. Add optional source, module_name, and pack_id query parameters
   (combined with AND) so a frontend / Manager can ask ?pack_id=foo
   instead of grep'ing through the whole grouped response. pack_id
   resolves against pyproject.project.name; entries without a parsed
   pyproject are naturally excluded from a pack_id query.

The grouping + filtering + module_path stripping moves into

odes.filter_node_startup_errors so the route handler is a one-liner and
the helper is unit-testable without spinning up an aiohttp app.

Tests: 5 new unit tests covering each filter branch, AND-combination, and
empty-result behaviour, plus an updated pyproject-metadata assertion that
checks the nested PyProjectConfig shape, plus a focused test for the
_prune_empty helper.

server.py

@@ -780,12 +780,26 @@ class PromptServer():
 
             ``module_path`` is stripped because the absolute on-disk path is
             internal detail that the frontend has no use for.
+
+            Optional query parameters narrow the response:
+
+            * ``source``        — only entries from this source bucket.
+            * ``module_name``   — only entries whose module name matches exactly.
+                                  (Folder name for directory-style packs, file
+                                  stem for single-file modules.)
+            * ``pack_id``       — only entries whose ``pyproject.project.name``
+                                  matches exactly. Entries without a parsed
+                                  pyproject.toml are skipped under this filter.
+
+            Filters are combined with AND. Filtering an empty / non-matching
+            result still returns ``{}`` with HTTP 200 rather than 404 — absence
+            of an error is a valid answer for this endpoint.
             """
-            grouped: dict[str, dict[str, dict]] = {}
-            for entry in nodes.NODE_STARTUP_ERRORS.values():
-                source = entry.get("source", "custom_nodes")
-                public_entry = {k: v for k, v in entry.items() if k != "module_path"}
-                grouped.setdefault(source, {})[entry["module_name"]] = public_entry
+            grouped = nodes.filter_node_startup_errors(
+                source=request.query.get("source"),
+                module_name=request.query.get("module_name"),
+                pack_id=request.query.get("pack_id"),
+            )
             return web.json_response(grouped)
 
         @routes.get("/api/jobs")