Prevent build artifacts from being cached

Add .npmignore to exclude build/ and bin/ directories from package
cache. This ensures native modules are always freshly built on the
target system, preventing MODULE_VERSION mismatches in Electron.

Fixes issue where yarn cache includes stale Node.js builds that
don't get rebuilt for Electron.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <[email protected]>

Author: rathboma

.npmignore

@@ -0,0 +1,12 @@
+# Don't include build artifacts in package/cache
+# These should be built on the target system
+build/
+bin/
+bin32/
+bin64/
+
+# Development files
+.github/
+test/
+*.log
+.DS_Store