fix: increase stream read timeout default to 120s, auto-raise for local LLMs (#6967)

Raise the default httpx stream read timeout from 60s to 120s for all
providers. Additionally, auto-detect local LLM endpoints (Ollama,
llama.cpp, vLLM) and raise the read timeout to HERMES_API_TIMEOUT
(1800s) since local models can take minutes for prefill on large
contexts before producing the first token.

The stale stream timeout already had this local auto-detection pattern;
the httpx read timeout was missing it — causing a hard 60s wall that
users couldn't find (HERMES_STREAM_READ_TIMEOUT was undocumented).

Changes:
- Default HERMES_STREAM_READ_TIMEOUT: 60s -> 120s
- Auto-detect local endpoints -> raise to 1800s (user override respected)
- Document HERMES_STREAM_READ_TIMEOUT and HERMES_STREAM_STALE_TIMEOUT
- Add 10 parametrized tests

Reported-by: Pavan Srinivas (@pavanandums)

run_agent.py

@@ -4433,7 +4433,17 @@ class AIAgent:
             """Stream a chat completions response."""
             import httpx as _httpx
             _base_timeout = float(os.getenv("HERMES_API_TIMEOUT", 1800.0))
-            _stream_read_timeout = float(os.getenv("HERMES_STREAM_READ_TIMEOUT", 60.0))
+            _stream_read_timeout = float(os.getenv("HERMES_STREAM_READ_TIMEOUT", 120.0))
+            # Local providers (Ollama, llama.cpp, vLLM) can take minutes for
+            # prefill on large contexts before producing the first token.
+            # Auto-increase the httpx read timeout unless the user explicitly
+            # overrode HERMES_STREAM_READ_TIMEOUT.
+            if _stream_read_timeout == 120.0 and self.base_url and is_local_endpoint(self.base_url):
+                _stream_read_timeout = _base_timeout
+                logger.debug(
+                    "Local provider detected (%s) — stream read timeout raised to %.0fs",
+                    self.base_url, _stream_read_timeout,
+                )
             stream_kwargs = {
                 **api_kwargs,
                 "stream": True,