chore: gitignore temp/ scratch dir and untrack it

temp/ is local scratch (probe drafts, JSON dumps, debug scripts). It was being
swept into every /save by sync.sh's git add -A. Now ignored + untracked (files
remain on disk; history unchanged).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.gitignore

@@ -92,3 +92,4 @@ projects/radio-show/audio-processor/*.egg-info/
 clients/internal-infrastructure/datto-bsod-case-2026-05-16.zip
 clients/internal-infrastructure/datto-bsod-case-2026-05-16/
 
+temp/