Run oxfmt across repo, add format script and ignore config

Format all non-generated files with oxfmt via `vp fmt`. Add
.oxfmtignore to skip bindings/ and wasm-pack output. Add npm
format script and update DEVELOPMENT.md docs.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src-web/postcss.config.cjs

@@ -1,7 +1,7 @@
 module.exports = {
   plugins: [
-    require('@tailwindcss/nesting')(require('postcss-nesting')),
-    require('tailwindcss'),
-    require('autoprefixer'),
-  ]
-}
+    require("@tailwindcss/nesting")(require("postcss-nesting")),
+    require("tailwindcss"),
+    require("autoprefixer"),
+  ],
+};