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)

website/docs/reference/environment-variables.md

@@ -278,6 +278,8 @@ For cloud sandbox backends, persistence is filesystem-oriented. `TERMINAL_LIFETI
 | `HERMES_HUMAN_DELAY_MAX_MS` | Custom delay range maximum (ms) |
 | `HERMES_QUIET` | Suppress non-essential output (`true`/`false`) |
 | `HERMES_API_TIMEOUT` | LLM API call timeout in seconds (default: `1800`) |
+| `HERMES_STREAM_READ_TIMEOUT` | Streaming socket read timeout in seconds (default: `120`). Auto-increased to `HERMES_API_TIMEOUT` for local providers. Increase if local LLMs time out during long code generation. |
+| `HERMES_STREAM_STALE_TIMEOUT` | Stale stream detection timeout in seconds (default: `180`). Auto-disabled for local providers. Triggers connection kill if no chunks arrive within this window. |
 | `HERMES_EXEC_ASK` | Enable execution approval prompts in gateway mode (`true`/`false`) |
 | `HERMES_ENABLE_PROJECT_PLUGINS` | Enable auto-discovery of repo-local plugins from `./.hermes/plugins/` (`true`/`false`, default: `false`) |
 | `HERMES_BACKGROUND_NOTIFICATIONS` | Background process notification mode in gateway: `all` (default), `result`, `error`, `off` |