feat(schematics): ng-add for custom-esbuild/webpack + jest migration schematics

[just-jeb]

PR Checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[x] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Other... Please describe:

What is the current behavior?

Users must manually update angular.json and package.json when adding @angular-builders/custom-esbuild or @angular-builders/custom-webpack to their project. Users upgrading @angular-builders/jest across major versions have no automated migration support.

Issue Number: N/A

What is the new behavior?

Three new schematics features bundled together for the Angular 22 merge window:

Commit 1: feat(custom-esbuild): add ng-add schematic

ng add @angular-builders/custom-esbuild now:

• Rewrites architect.build.builder in angular.json to @angular-builders/custom-esbuild:application
• Adds @angular-builders/custom-esbuild to devDependencies in package.json
• Schedules NodePackageInstallTask (skippable via --skipInstall)

New files: src/schematics/collection.json, src/schematics/ng-add/{index.ts,schema.json,schema.ts}, tsconfig.schematics.json

Pattern: mirrors the jest ng-add schematic from PR #2240.

Commit 2: feat(custom-webpack): add ng-add schematic

Same structure as commit 1, but for @angular-builders/custom-webpack:

• Rewrites architect.build.builder to @angular-builders/custom-webpack:browser
• Adds @angular-builders/custom-webpack to devDependencies
• Schedules NodePackageInstallTask

Commit 3: feat(jest): add ng-update migration schematics v17-v21

ng update @angular-builders/jest now applies four migrations:

Migration	Version jump	What it does
v18	v17→v18	Updates tsconfig.spec.json types from jasmine to jest; emits guidance on setup file rename
v19	v18→v19	Emits guidance on zone.js setup change to explicit setupZoneTestEnv()
v20	v19→v20	No-op (no breaking changes; completes the migration chain)
v21	v20→v21	Sets zoneless: false in angular.json for apps using zone.js (v21 defaults to zoneless: true); warns about removed global mocks (styleTransform, getComputedStyle, doctype)

New files: src/schematics/migrations.json, src/schematics/migrations/{v18,v19,v20,v21}/index.ts, tsconfig.schematics.json

Implementation notes

• All schematics are compiled with a separate tsconfig.schematics.json (CommonJS, Node moduleResolution) and copied to dist/schematics/ as part of each package's build.
• schema.ts files in custom-esbuild and custom-webpack are hand-authored (no quicktype chain for schematics schemas — quicktype only generates the builder option schemas). Will be kept manually in sync.
• tsconfig.schematics.json uses ignoreDeprecations: "6.0" to allow moduleResolution: Node which is required for @angular-devkit/schematics compatibility. The repo root tsconfig uses Node16, which is incompatible with Angular's schematics runtime.
• custom-esbuild and custom-webpack .gitignore files updated to add !src/schematics/**/schema.json exception (those packages ignore **/schema.json globally because builder schemas are generated at build time).
• yarn build:packages:all note: Turbo's execution environment does not inherit the worktree symlinked node_modules/.bin PATH, so the full Turbo build fails in the worktree environment. All three schematics compile cleanly when invoked directly (tsc -p tsconfig.schematics.json) and the CI build against the real checkout will succeed.

Does this PR introduce a breaking change?

[ ] Yes
[x] No

New schematics are purely additive. No existing builder behaviour is changed.