chore: remove accidentally-committed test-scratch files from repo root

dialog_out/, dlg2/, mxfdlg/, mxf_*.ti3 and scratch_c2.py were stray
outputs from dialog/i1Profiler testing; nothing references them. Added
.gitignore rules so they don't return.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: itsab1989

.gitignore

@@ -66,3 +66,10 @@ assets/app_icon.ico
 
 # Frozen schema-1 test fixture (#127) — must override the binary ignores above
 !tests/golden/project_v1/**
+
+# Accidental test-scratch output at repo root
+/dialog_out/
+/dlg2/
+/mxfdlg/
+/mxf_*.ti3
+/scratch_*.py