Replace gulp by nx-infra-plugin in devextreme-scss

[GoodDayForSurf]

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[Copilot]

Pull request overview

This PR migrates the devextreme-scss theme build pipeline from Gulp-based tasks to a dedicated Nx Infra Plugin executor, aiming to make SCSS theme compilation and asset copying fully Nx-driven and cacheable across the monorepo.

Changes:

• Removed devextreme-scss Gulp build implementation (gulpfile + style compiler + gulp data-uri) and related dependencies.
• Added a new devextreme-nx-infra-plugin:scss-build executor that generates SCSS bundles and compiles/minifies CSS (with license header + charset handling).
• Updated devextreme, ThemeBuilder, and CI workflow wiring to use Nx targets for building themes.

Reviewed changes

Copilot reviewed 14 out of 15 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
pnpm-lock.yaml	Removes Gulp-related dependencies from the lockfile for devextreme-scss.
packages/nx-infra-plugin/src/executors/scss-build/schema.ts	Adds TypeScript schema for the new SCSS build executor options.
packages/nx-infra-plugin/src/executors/scss-build/schema.json	Adds JSON schema for executor configuration / validation.
packages/nx-infra-plugin/src/executors/scss-build/executor.ts	Implements SCSS bundle generation, compilation, postcss/autoprefixer, clean-css minification, watch mode, and asset copying logic.
packages/nx-infra-plugin/src/executors/scss-build/executor.e2e.spec.ts	Adds an E2E test validating output, license header, and minification profile behavior.
packages/nx-infra-plugin/executors.json	Registers the new scss-build executor in the plugin.
packages/devextreme/package.json	Switches build-themes script from Gulp to Nx-driven devextreme-scss targets.
packages/devextreme-themebuilder/src/modules/post-compiler.ts	Improves @charset + info header handling; introduces an optional mode to append the info header at the end.
packages/devextreme-themebuilder/src/modules/compile-manager.ts	Uses the new addInfoHeader(..., true) behavior for ThemeBuilder output.
packages/devextreme-scss/project.json	Replaces Gulp scripts/inputs with Nx targets: clean, build themes (all/ci), copy assets, and watch.
packages/devextreme-scss/package.json	Removes Gulp-related devDependencies and updates scripts to call Nx targets.
packages/devextreme-scss/gulpfile.js	Deleted (Gulp entrypoint no longer used).
packages/devextreme-scss/build/style-compiler.js	Deleted (legacy SCSS build pipeline).
packages/devextreme-scss/build/gulp-data-uri.js	Deleted (legacy data-uri implementation).
.github/workflows/themebuilder_tests.yml	Updates ThemeBuilder CI to build “etalon bundles” via Nx instead of Gulp.

Files not reviewed (1)

• pnpm-lock.yaml: Language not supported