docs: add import organization guidelines to AGENTS.md

AGENTS.md

@@ -1,5 +1,11 @@
 # Agent Instructions
 
+## Import Organization
+
+- **Keep all imports at the top of the file.** Never add imports inside functions, methods, or conditional blocks.
+- Use absolute imports for project modules (e.g., `from gitea.models import IssueModel`).
+- Remove unused imports when editing files.
+
 ## Python Type Hints (REQUIRED)
 
 - **All functions must have type hints** for parameters and return types.