#7824: fix(ui): remove --prod install flag that causes vite not found error

The build action was using pnpm install --prod with NODE_ENV=production, which skips devDependencies. This caused the build to fail with 'vite not found' or silent exit code 1 errors. The fix removes the --prod flag and NODE_ENV=production override, ensuring all dependencies (including devDependencies needed for the build) are installed. Fixes #7104 <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR updates the UI helper script (`scripts/ui.js`) to always install full dependencies before running `build`/`test`, removing the prior `pnpm install --prod` + `NODE_ENV=production` behavior that skipped `devDependencies` and could lead to missing build tools like `vite`. The change aligns the install step with the script’s existing `depsInstalled()` check (which already requires `vite`/`vitest` for build/test) so CI and local builds don’t fail due to omitted dev tooling. <h3>Confidence Score: 5/5</h3> - This PR is safe to merge with minimal risk; it simplifies dependency installation to avoid missing build tooling. - Change is localized to `scripts/ui.js` and replaces conditional prod-only installs with a standard install, matching the script’s existing dependency checks. No behavior changes beyond ensuring devDependencies are installed when running build/test/dev after a missing-deps state. - No files require special attention <!-- greptile_other_comments_section --> _{(3/5) Reply to the agent's comments like "Can you suggest a fix for this @greptileai?" or ask follow-up questions!} <!-- /greptile_comment -->