fix(codex): size and propagate timeouts for Responses-API requests; lower stale defaults

Codex / Responses-API requests had three latent timeout bugs that combined
into the long silent hangs reported on #21444:

1. The non-stream stale-call detector estimated context tokens from
   ``api_kwargs["messages"]`` only. Codex / Responses-API payloads carry
   their conversational load in ``input`` (with ``instructions`` and
   ``tools``), so every Codex turn logged ``context=~0 tokens`` and the
   detector never applied its >50k / >100k tier bumps.

2. ``providers.<id>.request_timeout_seconds`` was silently dropped on the
   main Codex path. The chat_completions path and the auxiliary Codex
   adapter both forwarded it; the main path skipped it through three
   places (``build_api_kwargs``, ``ResponsesApiTransport.build_kwargs``,
   ``_preflight_codex_api_kwargs``).

3. The streaming stale detector had the same payload-shape bug for
   ``codex_responses`` requests, which route through the non-streaming
   detector (it's the path that emits the user-facing
   "No response from provider for 300s (non-streaming, ...)" warning that
   reporters keep pasting).

This commit:

- Adds ``estimate_request_context_tokens`` in ``chat_completion_helpers``,
  used by both the non-stream and stream detectors. Handles ``messages``
  (Chat Completions), ``input + instructions + tools`` (Responses API),
  bare lists, and an unknown-dict fallback.
- Forwards ``timeout`` through ``ResponsesApiTransport.build_kwargs``
  and ``_preflight_codex_api_kwargs`` (with guards against
  zero/negative/inf/bool values), and wires
  ``_resolved_api_call_timeout()`` into the Codex branch of
  ``build_api_kwargs``.
- Lowers the implicit non-stream stale defaults so fallback providers
  kick in faster when upstream stalls:
    * base   300s -> 90s
    * >50k   450s -> 150s
    * >100k  600s -> 240s
  These only apply when the user has *not* set
  ``providers.<id>.stale_timeout_seconds`` or
  ``HERMES_API_CALL_STALE_TIMEOUT``. Explicit config still wins.
- Adds regression tests for the estimator shapes, the new defaults, the
  context-tier scaling, transport timeout pass-through, and preflight
  timeout pass-through / rejection of invalid values.

Closes #21444
Supersedes #21652 #24126 #31855

Co-authored-by: Hoang V. Pham <26063003+hehehe0803@users.noreply.github.com>

agent/codex_responses_adapter.py

@@ -745,7 +745,7 @@ def _preflight_codex_api_kwargs(
         "model", "instructions", "input", "tools", "store",
         "reasoning", "include", "max_output_tokens", "temperature",
         "tool_choice", "parallel_tool_calls", "prompt_cache_key", "service_tier",
-        "extra_headers", "extra_body",
+        "extra_headers", "extra_body", "timeout",
     }
     normalized: Dict[str, Any] = {
         "model": model,
@@ -771,6 +771,13 @@ def _preflight_codex_api_kwargs(
     max_output_tokens = api_kwargs.get("max_output_tokens")
     if isinstance(max_output_tokens, (int, float)) and max_output_tokens > 0:
         normalized["max_output_tokens"] = int(max_output_tokens)
+    timeout = api_kwargs.get("timeout")
+    if (
+        isinstance(timeout, (int, float))
+        and not isinstance(timeout, bool)
+        and 0 < float(timeout) < float("inf")
+    ):
+        normalized["timeout"] = float(timeout)
     temperature = api_kwargs.get("temperature")
     if isinstance(temperature, (int, float)):
         normalized["temperature"] = float(temperature)