📝 Add diff context explanation to commit message prompt

Improves AI understanding of git diff format by including the
DIFF_CONTEXT_EXPLANATION constant. This helps generate more accurate
commit messages by clarifying how to interpret diff symbols.

Author: Nick Sullivan

aicodebot/prompts.py

@@ -350,6 +350,10 @@ def generate_files_context(files):
 • For simple changes, omit the body entirely if summary is sufficient
 • Never repeat information that's obvious from reading the diff
 
+"""
+    + DIFF_CONTEXT_EXPLANATION
+    + """
+
 SAMPLE EXCELLENCE:
 🔐 Implement user authentication with JWT tokens