fix: pin tempfile output dir in CODE_FILE_HANDLING system instruction

- Replace multi-rule prompt with single sticky instruction
- Inject `tempfile.tempdir = "/app/generated_files"` at top of all
  file-generating scripts to prevent phantom file failures in sandbox

Author: Francisco

src/api/entities_api/orchestration/instructions/definitions.py

@@ -408,6 +408,14 @@
         "4. **FILE FACTORY:** You have NATIVE capabilities to generate downloadable files. "
         "If a user wants a report, summary, or data, you MUST write code to create a .docx, .csv, or .xlsx file."
     ),
+    "CODE_FILE_HANDLING": (
+        "\n🔹 [STICKY SYSTEMS INSTRUCTION — PERMANENT]\n"
+        "All Python code execution contexts must inject the following line at the top of every script "
+        "that generates files using libraries that rely on tempfile "
+        "(e.g., python-docx, openpyxl, matplotlib, pandas with Excel output):\n\n"
+        "import tempfile; tempfile.tempdir = \"/app/generated_files\"\n\n"
+        "This ensures all temporary and final files are written to the correct sandbox output directory."
+    ),
     "ADVANCED_ANALYSIS": (
         "\n1. Always save generated files locally during code execution.\n"
         "2. Do not display, preview, or open files in memory.\n"

src/api/entities_api/orchestration/instructions/include_lists.py

@@ -1,11 +1,11 @@
-from entities_api.orchestration.instructions.definitions import \
-    LEVEL_3_WEB_USE_INSTRUCTIONS
+from entities_api.orchestration.instructions.definitions import LEVEL_3_WEB_USE_INSTRUCTIONS
 
 L2_INSTRUCTIONS = [
     "TOOL_USAGE_PROTOCOL",
     "FUNCTION_CALL_FORMATTING",
     "FUNCTION_CALL_WRAPPING",
     "CODE_INTERPRETER",  # code interpreter
+    "CODE_FILE_HANDLING",
 ]
 
 L3_INSTRUCTIONS = [
@@ -14,6 +14,7 @@
     "TOOL_DECISION_PROTOCOL",
     "L3_PARALLEL_EXECUTION",
     "CODE_INTERPRETER"  # code interprete
+    "CODE_FILE_HANDLING",  # code interpreter
     "CITATION_PROTOCOL",
     "TOOL_USAGE_PROTOCOL",
     "FUNCTION_CALL_FORMATTING",