fix: patch three critical defects from the SDK review

- local delete_collection: validate the collection name before rmtree.
  An unvalidated name like "../.." escaped files_dir and deleted
  arbitrary directories (path traversal).

- legacy page_index(): restore the node_id/summary/text/description
  enhancements. IndexConfig now carries booleans (pydantic coerces the
  legacy 'yes'/'no' strings at the boundary), but page_index_main still
  compared `opt.if_add_node_id == 'yes'` — always False — so every
  enhancement was silently skipped for legacy-API callers. Conditions
  now branch on the booleans, matching pageindex/index/page_index.py.

- LegacyCloudAPI._request: bound every request with a timeout
  (30s, 120s read timeout for streamed responses) so a dead connection
  can't hang legacy submit/poll/chat callers forever. The legacy
  contract tests pinned the missing timeout; updated to pin its
  presence instead.

Adds regression tests: path-traversal rejection, 'yes'/'no' -> bool
coercion, and timeout assertions.

Claude-Session: https://claude.ai/code/session_01Kx5DgKbhK1N8autqXH8SmS

pageindex/cloud_api.py

@@ -21,6 +21,10 @@ class LegacyCloudAPI:
         return {"api_key": self.api_key}
 
     def _request(self, method: str, path: str, error_prefix: str, **kwargs) -> requests.Response:
+        # Always bound the request so a dead connection can't hang callers
+        # forever. Streamed responses get a longer read timeout since it
+        # applies between chunks, not to the whole response.
+        kwargs.setdefault("timeout", 120 if kwargs.get("stream") else 30)
         try:
             response = requests.request(
                 method,