refactor: concise prompts - 5-10 words, precise but brief

- Tool description: 'Describe what this PR does in 5-10 words'
- SYSTEM_PROMPT: minimal 4-line instructions
- User message: simple and direct
- Example: 'Fix null pointer in login when email is empty'
- Tests: 1197 pass

Author: Atlas

src/swe_forge/llm/tools.py

@@ -125,21 +125,20 @@ def submit_tests_tool_schema() -> ToolDefinition:
 def set_dataset_prompt_tool_schema() -> ToolDefinition:
     """Create the set_dataset_prompt tool schema.
     
-    This tool is used by the agent to set a natural description of the PR changes.
-    The prompt describes what the PR does, in natural language.
+    This tool is used by the agent to set a concise description of what the PR does.
     
     Returns:
         ToolDefinition for the set_dataset_prompt tool.
     """
     return ToolDefinition.create(
         name="set_dataset_prompt",
-        description="Set a natural language description of what this PR does. Use this to describe the changes in simple terms.",
+        description="Describe what this PR does in 5-10 words. Be specific but brief.",
         parameters={
             "type": "object",
             "properties": {
                 "prompt": {
                     "type": "string",
-                    "description": "Natural description of the PR changes (e.g., 'Fixes null pointer exception in login when email is empty')",
+                    "description": "Short description (e.g., 'Fix null pointer in login when email is empty' or 'Add dark mode toggle to settings')",
                 },
             },
             "required": ["prompt"],

src/swe_forge/swe/test_generator.py

@@ -49,10 +49,12 @@
 # System Prompt
 # ─────────────────────────────────────────────────────────────────────────────
 
-SYSTEM_PROMPT = """Analyze the GitHub PR and write verification tests.
+SYSTEM_PROMPT = """Write tests for this PR.
 
-First, describe what the PR does using set_dataset_prompt.
-Then explore the repo, install dependencies, write tests, and submit."""
+1. Call set_dataset_prompt with a short description (5-10 words)
+2. Explore and install dependencies  
+3. Write tests
+4. Submit"""
 
 
 # ─────────────────────────────────────────────────────────────────────────────
@@ -486,11 +488,11 @@ def _truncate(self, s: str, max_len: int = 4000) -> str:
 
     def _build_user_message(self, task: SweTask) -> str:
         """Build the initial user message for the agent."""
-        return f"""PR in {task.repo}:
+        return f"""{task.repo}
 
 {self._truncate(task.patch, 4000)}
 
-Describe what this PR does, then write tests."""
+Use set_dataset_prompt first, then write tests."""
 
     def _test_commands_for_language(self, language: str) -> tuple[list[str], list[str]]:
         """Get suggested build and test commands for a language.