Importing a CommonJS package breaks the production build

• `npm run build` fails with `SyntaxError: The requested module '/node_modules/.vite/deps/proj4.js?v=9a1c3f2e' does not provide an export named 'default'`
• Webpack logs `WARNING in ./src/geo/transform.js "export 'default' (imported as 'proj4') was not found in 'proj4'`
• `npm run dev` serves the same page without any error, so the break only appears in the bundle

1. Read the package's package.json: a `main` entry with no `module` or `exports` field means CJS
2. Run `node -e "const p=require('proj4'); console.log(typeof p, Object.keys(p).slice(0,5));"` and compare with the dynamic `import('proj4')` shape
3. Search the build log for `commonjs` or `optimizeDeps` mentions
4. Try a namespace import and read `.default` to confirm the interop assumption
5. Rebuild after adding the package to `optimizeDeps.include`

Add `proj4` to `optimizeDeps.include` and set `build.commonjsOptions.transformMixedEsModules: true`, then use `import proj4 from 'proj4'`; when interop still fails, fall back to `import * as proj4Module from 'proj4'` plus `const proj4 = proj4Module.default || proj4Module`.

error during build:
SyntaxError: The requested module '/node_modules/.vite/deps/proj4.js?v=9a1c3f2e'
does not provide an export named 'default'

WARNING in ./src/geo/transform.js
"export 'default' (imported as 'proj4') was not found in 'proj4'

• Writing named imports such as `import { transform } from 'proj4'`; CJS properties are not statically analyzable named exports
• Editing application code while ignoring the package format, which keeps failing until the optimizer handles the CJS entry