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/config/__init__.py

@@ -0,0 +1,12 @@
+from strix.config.config import (
+    Config,
+    apply_saved_config,
+    save_current_config,
+)
+
+
+__all__ = [
+    "Config",
+    "apply_saved_config",
+    "save_current_config",
+]

strix/config/config.py

@@ -0,0 +1,119 @@
+import json
+import os
+from pathlib import Path
+from typing import Any
+
+
+class Config:
+    """Configuration Manager for Strix."""
+
+    # LLM Configuration
+    strix_llm = "openai/gpt-5"
+    llm_api_key = None
+    llm_api_base = None
+    openai_api_base = None
+    litellm_base_url = None
+    ollama_api_base = None
+    strix_reasoning_effort = "high"
+    llm_timeout = "300"
+    llm_rate_limit_delay = "4.0"
+    llm_rate_limit_concurrent = "1"
+
+    # Tool & Feature Configuration
+    perplexity_api_key = None
+    strix_disable_browser = "false"
+
+    # Runtime Configuration
+    strix_image = "ghcr.io/usestrix/strix-sandbox:0.1.10"
+    strix_runtime_backend = "docker"
+    strix_sandbox_execution_timeout = "500"
+    strix_sandbox_connect_timeout = "10"
+
+    # Telemetry
+    strix_telemetry = "1"
+
+    @classmethod
+    def _tracked_names(cls) -> list[str]:
+        return [
+            k
+            for k, v in vars(cls).items()
+            if not k.startswith("_") and k[0].islower() and (v is None or isinstance(v, str))
+        ]
+
+    @classmethod
+    def tracked_vars(cls) -> list[str]:
+        return [name.upper() for name in cls._tracked_names()]
+
+    @classmethod
+    def get(cls, name: str) -> str | None:
+        env_name = name.upper()
+        default = getattr(cls, name, None)
+        return os.getenv(env_name, default)
+
+    @classmethod
+    def config_dir(cls) -> Path:
+        return Path.home() / ".strix"
+
+    @classmethod
+    def config_file(cls) -> Path:
+        return cls.config_dir() / "cli-config.json"
+
+    @classmethod
+    def load(cls) -> dict[str, Any]:
+        path = cls.config_file()
+        if not path.exists():
+            return {}
+        try:
+            with path.open("r", encoding="utf-8") as f:
+                data: dict[str, Any] = json.load(f)
+                return data
+        except (json.JSONDecodeError, OSError):
+            return {}
+
+    @classmethod
+    def save(cls, config: dict[str, Any]) -> bool:
+        try:
+            cls.config_dir().mkdir(parents=True, exist_ok=True)
+            with cls.config_file().open("w", encoding="utf-8") as f:
+                json.dump(config, f, indent=2)
+        except OSError:
+            return False
+        else:
+            return True
+
+    @classmethod
+    def apply_saved(cls) -> dict[str, str]:
+        saved = cls.load()
+        env_vars = saved.get("env", {})
+        applied = {}
+
+        for var_name, var_value in env_vars.items():
+            if var_name in cls.tracked_vars() and not os.getenv(var_name):
+                os.environ[var_name] = var_value
+                applied[var_name] = var_value
+
+        return applied
+
+    @classmethod
+    def capture_current(cls) -> dict[str, Any]:
+        env_vars = {}
+        for var_name in cls.tracked_vars():
+            value = os.getenv(var_name)
+            if value:
+                env_vars[var_name] = value
+        return {"env": env_vars}
+
+    @classmethod
+    def save_current(cls) -> bool:
+        existing = cls.load().get("env", {})
+        current = cls.capture_current().get("env", {})
+        merged = {**existing, **current}
+        return cls.save({"env": merged})
+
+
+def apply_saved_config() -> dict[str, str]:
+    return Config.apply_saved()
+
+
+def save_current_config() -> bool:
+    return Config.save_current()