fix: add timeout handling for Docker operations and improve error messages

- Add SandboxInitializationError exception for sandbox/Docker failures
- Add 60-second timeout to Docker client initialization
- Add _exec_run_with_timeout() method using ThreadPoolExecutor for exec_run calls
- Catch ConnectionError and Timeout exceptions from requests library
- Add _handle_sandbox_error() and _handle_llm_error() methods in base_agent.py
- Handle sandbox_error_details tool in TUI for displaying errors
- Increase TUI truncation limits for better error visibility
- Update all Docker error messages with helpful hint:
  'Please ensure Docker Desktop is installed and running, and try running strix again.'

strix/runtime/__init__.py

@@ -3,6 +3,15 @@ import os
 from .runtime import AbstractRuntime
 
 
+class SandboxInitializationError(Exception):
+    """Raised when sandbox initialization fails (e.g., Docker issues)."""
+
+    def __init__(self, message: str, details: str | None = None):
+        super().__init__(message)
+        self.message = message
+        self.details = details
+
+
 def get_runtime() -> AbstractRuntime:
     runtime_backend = os.getenv("STRIX_RUNTIME_BACKEND", "docker")
 
@@ -16,4 +25,4 @@ def get_runtime() -> AbstractRuntime:
     )
 
 
-__all__ = ["AbstractRuntime", "get_runtime"]
+__all__ = ["AbstractRuntime", "SandboxInitializationError", "get_runtime"]