fix(agent): align LLM wall timeout with sustained goals for main + subagents

Centralize runner_wall_llm_timeout_s in session goal_state metadata helpers so
spawned subagents inherit the same policy as AgentLoop without coupling to
long_task. Pass optional resolver into SubagentManager and add tests.

Co-authored-by: Cursor <cursoragent@cursor.com>

nanobot/session/goal_state.py

@@ -1,8 +1,8 @@
 """Session metadata helpers for sustained goals (e.g. ``long_task`` / ``complete_goal``).
 
 Tools set ``metadata[GOAL_STATE_KEY]``. Reads accept the legacy session key ``thread_goal``
-for older sessions. The agent uses ``goal_state_runtime_lines`` and
-``goal_state_ws_blob`` without importing tool implementations.
+for older sessions. Callers use ``goal_state_runtime_lines``, ``goal_state_ws_blob``, and
+``runner_wall_llm_timeout_s`` without importing tool implementations.
 """
 
 from __future__ import annotations
@@ -10,6 +10,8 @@ from __future__ import annotations
 import json
 from typing import Any, Mapping, MutableMapping
 
+from nanobot.session.manager import SessionManager
+
 GOAL_STATE_KEY = "goal_state"
 # Older builds stored the same JSON blob under this key.
 _LEGACY_GOAL_STATE_SESSION_KEY = "thread_goal"
@@ -89,3 +91,21 @@ def goal_state_ws_blob(metadata: Mapping[str, Any] | None) -> dict[str, Any]:
             blob["objective"] = objective
         return blob
     return {"active": False}
+
+
+def runner_wall_llm_timeout_s(
+    sessions: SessionManager,
+    session_key: str | None,
+    *,
+    metadata: Mapping[str, Any] | None = None,
+) -> float | None:
+    """Wall-clock cap for :class:`~nanobot.agent.runner.AgentRunner` when streaming an LLM.
+
+    Returns ``0.0`` to disable ``asyncio.wait_for`` around the request when a sustained goal is
+    active; ``None`` means use ``NANOBOT_LLM_TIMEOUT_S``. Pass in-memory ``metadata`` when the
+    caller already holds :attr:`~nanobot.session.manager.Session.metadata` for this turn.
+    """
+    meta: Mapping[str, Any] | None = metadata
+    if meta is None and session_key:
+        meta = sessions.get_or_create(session_key).metadata
+    return 0.0 if sustained_goal_active(meta) else None