fix: Update Engineer to use dynamic prompt getter

- Remove ENGINEER_SYSTEM_PROMPT constant import
- Use get_engineer_system_prompt() function for per-request evaluation
- Ensures correct sandbox environment detection on HuggingFace Spaces

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app/agents/engineer.py

@@ -16,7 +16,7 @@ from app.core.llm_provider import LLMProviderFactory
 from app.core.logging import get_logger
 from app.core.exceptions import EngineerAgentError
 from app.agents.prompts import (
-    ENGINEER_SYSTEM_PROMPT,
+    get_engineer_system_prompt,
     ENGINEER_USER_PROMPT_TEMPLATE,
     ENGINEER_RETRY_PROMPT_TEMPLATE
 )
@@ -57,19 +57,21 @@ class EngineerAgent:
         # Get LLM provider
         self.llm = LLMProviderFactory.create_from_settings()
 
-        # Create prompt templates (we'll choose at runtime)
-        self.normal_prompt = ChatPromptTemplate.from_messages([
-            ("system", ENGINEER_SYSTEM_PROMPT),
-            ("human", ENGINEER_USER_PROMPT_TEMPLATE)
-        ])
-
-        self.retry_prompt = ChatPromptTemplate.from_messages([
-            ("system", ENGINEER_SYSTEM_PROMPT),
-            ("human", ENGINEER_RETRY_PROMPT_TEMPLATE)
-        ])
+        # Store prompt templates - system prompt is generated dynamically per-request
+        # to ensure correct sandbox environment detection
+        self._user_prompt_template = ENGINEER_USER_PROMPT_TEMPLATE
+        self._retry_prompt_template = ENGINEER_RETRY_PROMPT_TEMPLATE
 
         logger.info("Engineer Agent initialized")
 
+    def _get_prompt(self, is_retry: bool = False) -> ChatPromptTemplate:
+        """Get prompt template with dynamic system prompt."""
+        human_template = self._retry_prompt_template if is_retry else self._user_prompt_template
+        return ChatPromptTemplate.from_messages([
+            ("system", get_engineer_system_prompt()),  # Dynamic per-request
+            ("human", human_template)
+        ])
+
     def refresh_llm(self):
         """Refresh LLM provider with latest settings from Redis."""
         self.llm = LLMProviderFactory.create_from_settings()
@@ -154,7 +156,8 @@ class EngineerAgent:
                     }
                 )
 
-                chain = self.retry_prompt | self.llm.generate | StrOutputParser()
+                prompt = self._get_prompt(is_retry=True)
+                chain = prompt | self.llm.generate | StrOutputParser()
 
                 code = await chain.ainvoke({
                     "function_name": function_name,
@@ -170,7 +173,8 @@ class EngineerAgent:
                     extra={"function_name": function_name}
                 )
 
-                chain = self.normal_prompt | self.llm.generate | StrOutputParser()
+                prompt = self._get_prompt(is_retry=False)
+                chain = prompt | self.llm.generate | StrOutputParser()
 
                 code = await chain.ainvoke({
                     "function_name": function_name,