🚩 /api/v2/catalog still async def while now calling sync stat()
`/api/v2/catalog` was left as `async def` when the rest of Tier 1 was
converted, on the assumption it was lightweight. The new
`_materialized_size_hint` populator added in this PR calls
`Path.stat()` / `Path.exists()` for every visible row to bucket the
parquet size — on a local FS that's microseconds, but on a
network-mounted DATA_DIR (NFS / CIFS / GCS-FUSE) those syscalls
can block the event loop. Convert to plain `def` so FastAPI
auto-offloads to the thread pool, mirroring /api/query etc.
🔴 stream_download translates HTTPStatusError as generic transport error
`response.raise_for_status()` inside the retry loop raises
`httpx.HTTPStatusError` on 4xx/5xx. After retries exhaust, the new
`isinstance(last_exc, httpx.HTTPError)` check at line 219 was eating
the status code: HTTPStatusError is a subclass of HTTPError, so the
generic transport translation produced "Unexpected error: HTTPStatusError"
instead of the informative "Client error '401 Unauthorized' for url …"
that callers expect. Fix: short-circuit HTTPStatusError before the
HTTPError branch — it re-raises verbatim so the caller's status-code
handling + the rich server error body (e.g. 401 expired token, 403
cross_project_forbidden) reach the analyst.
api_get / api_post / api_delete / api_patch don't have the same bug:
httpx Client.get/etc. don't raise HTTPStatusError unless the caller
explicitly calls .raise_for_status(), and our wrappers don't.
Only stream_download does, hence the targeted fix there.