QUICHE_H3_ERR_STREAM_BLOCKED issue

In curl, we added tests with large request headers and observe unexpected behaviour with quiche. Maybe we are holding it wrong. The case is simple, a request with ~64KB headers in total calls:

```
id = quiche_h3_send_request(h3c, qconn, nva, nheader, FALSE);
```

and `QUICHE_H3_ERR_STREAM_BLOCKED` is returned.

Usually, as we interpreted the documentation, this should indicate a temporary condition, to be retried later. But this error is permanent. How should we handle this case? Thank you for your support.

Start with the QUICHE_H3_ERR_STREAM_BLOCKED documentation and the quiche_h3_send_request entry point for requests with large headers. Trace how the ~64KB-header case is handled and compare the documented retry semantics with the observed permanent error. Done means the expected handling or limitation is established and clearly documented or reproducibly corrected.

Written by the indexing model from the issue text.