chore: stop tracking .qwen-agent-sessions/ and FACT.md

These files are local-only artifacts committed before .gitignore
rules existed. Add .cherry_migration/ and FACT.md to .gitignore.

Author: StarsailsClover

.gitignore

@@ -48,3 +48,7 @@ aprism-libs/
 
 # Session archives (local only, not distributed)
 .qwen-agent-sessions/
+.cherry_migration/
+
+# Project tracking (local only, not distributed)
+FACT.md