Route build outputs to dist/ and commit release artifacts

build.ps1 now always packages the .vsix and writes both artifacts to
dist/. Added .vscodeignore so the .vsix excludes Go source, TS source,
and other dev-only files.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.vscodeignore

@@ -0,0 +1,11 @@
+.git/**
+.vscode/**
+.gitignore
+standalone/**
+dist/**
+src/**
+out/**/*.map
+build.ps1
+tsconfig.json
+**/*.vsix
+node_modules/.cache/**