feat: add centralized Config class with auto-save to ~/.strix/cli-config.json

- Add Config class with all env var defaults in one place
- Auto-load saved config on startup (env vars take precedence)
- Auto-save config after successful LLM warm-up
- Replace scattered os.getenv() calls with Config.get()

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

strix/tools/__init__.py

@@ -1,5 +1,7 @@
 import os
 
+from strix.config import Config
+
 from .executor import (
     execute_tool,
     execute_tool_invocation,
@@ -22,9 +24,9 @@ from .registry import (
 
 SANDBOX_MODE = os.getenv("STRIX_SANDBOX_MODE", "false").lower() == "true"
 
-HAS_PERPLEXITY_API = bool(os.getenv("PERPLEXITY_API_KEY"))
+HAS_PERPLEXITY_API = bool(Config.get("perplexity_api_key"))
 
-DISABLE_BROWSER = os.getenv("STRIX_DISABLE_BROWSER", "false").lower() == "true"
+DISABLE_BROWSER = (Config.get("strix_disable_browser") or "false").lower() == "true"
 
 if not SANDBOX_MODE:
     from .agents_graph import *  # noqa: F403

strix/tools/executor.py

@@ -4,6 +4,8 @@ from typing import Any
 
 import httpx
 
+from strix.config import Config
+
 
 if os.getenv("STRIX_SANDBOX_MODE", "false").lower() == "false":
     from strix.runtime import get_runtime
@@ -17,8 +19,8 @@ from .registry import (
 )
 
 
-SANDBOX_EXECUTION_TIMEOUT = float(os.getenv("STRIX_SANDBOX_EXECUTION_TIMEOUT", "500"))
-SANDBOX_CONNECT_TIMEOUT = float(os.getenv("STRIX_SANDBOX_CONNECT_TIMEOUT", "10"))
+SANDBOX_EXECUTION_TIMEOUT = float(Config.get("strix_sandbox_execution_timeout"))  # type: ignore[arg-type]
+SANDBOX_CONNECT_TIMEOUT = float(Config.get("strix_sandbox_connect_timeout"))  # type: ignore[arg-type]
 
 
 async def execute_tool(tool_name: str, agent_state: Any | None = None, **kwargs: Any) -> Any: