chore(repo): normalize line endings and extend ignore boundary

Add .gitattributes with '* text=auto eol=lf' so Windows CRLF working
copies no longer surface as whole-file content changes; 37 tracked files
had flipped LF->CRLF with zero content change.

Ignore /tmp/ session scratch and research/experiments/node_modules, a
Windows junction git records as a symlink so **/node_modules/ misses it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016yuKikAXbByLvsUnh55SRd

.gitignore

@@ -43,3 +43,9 @@ Thumbs.db
 *.pth
 *.pt
 *.onnx
+
+# Session scratch
+/tmp/
+
+# Windows junction git sees as a symlink, so **/node_modules/ misses it
+/research/experiments/node_modules