Fix doubled workspace path when LLM passes absolute-style relative paths

resolve_safe_path now detects when the LLM passes the workspace root as
a relative path (e.g. "home/user/project/file.py") and strips the prefix
before joining. Also updated the system prompt to explicitly instruct the
model to use relative paths for all tool arguments.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/agent/loop.py

@@ -57,7 +57,10 @@ class AgentLoop:
             "You are SneakyCode, a local AI coding agent. "
             "You help users with software engineering tasks by reading files, "
             "searching code, and answering questions about their project.\n\n"
-            f"Workspace root: {self._config.agent.workspace_root}\n\n"
+            f"Workspace root: {self._config.agent.workspace_root}\n"
+            "IMPORTANT: All tool path arguments must be RELATIVE to the workspace root. "
+            'Use "." for the root, "app/main.py" for files, "app/" for subdirectories. '
+            "Never pass absolute paths or the workspace root path itself.\n\n"
             "Available tools: " + ", ".join(tool_names) + "\n\n"
             "When you have fully completed the user's request, call the `finish` tool "
             "with a brief summary. If you can answer directly without tools, just respond "