Chore: Gulp clean task migration

[ajivanyandev]

No description provided.

[Copilot]

Pull request overview

Migrates the gulp clean task in packages/devextreme to delegate to the existing clean:artifacts Nx target, completing the gulp-to-Nx migration pattern already used for transpile, vectormap, aspnet, etc. The Nx target's exclusion list is extended to preserve artifacts/npm/devextreme-dist, matching the previous del.sync preservation behavior.

Changes:

• Replaces the del.sync-based gulp clean body with shell.task('pnpm nx clean:artifacts devextreme') and removes the now-unused gulp-cache import.
• Adds ./artifacts/npm/devextreme-dist to clean:artifacts.excludePatterns so the devextreme-dist package output is preserved across cleans (matches prior gulp behavior).
• Documents the migration in .github/copilot-instructions.md and adds a "Migrated gulp tasks" section to packages/nx-infra-plugin/AGENTS.md.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
packages/devextreme/gulpfile.js	Replaces gulp clean implementation with a shell.task delegating to Nx; drops gulp-cache import.
packages/devextreme/project.json	Adds ./artifacts/npm/devextreme-dist to clean:artifacts exclusions to preserve dist output.
.github/copilot-instructions.md	Updates build-pipeline description to mention the Nx clean step and the gulp delegate.
packages/nx-infra-plugin/AGENTS.md	Adds a "Migrated gulp tasks" section documenting the migration pattern.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.