chore: Switch from Lerna and Yarn 1 to NPM (mobxjs#4646)

* Replace lerna with npm / yarn

* Replace yarn 1 with npm

* Keep mobx-undecorate CLI diff focused

* Add changeset for mobx-undecorate CLI fix

Author: kubk

.changeset/npm-workspace-cli-resolution.md

@@ -0,0 +1,5 @@
+---
+"mobx-undecorate": patch
+---
+
+Fix CLI resolution of the bundled jscodeshift binary when dependencies are hoisted by npm workspaces.

.github/PULL_REQUEST_TEMPLATE.md

@@ -14,7 +14,7 @@
 
 -   [ ] Added/updated unit tests
 -   [ ] Updated `/docs`. For new functionality, at least `API.md` should be updated
--   [ ] Verified that there is no significant performance drop (`yarn mobx test:performance`)
+-   [ ] Verified that there is no significant performance drop (`npm -w mobx run test:performance`)
 
 <!--
     Feel free to ask help with any of these boxes!

.github/workflows/build_and_test.yml

@@ -21,25 +21,25 @@ jobs:
           node-version: 24
 
       - name: Install Dependencies
-        run: yarn --frozen-lockfile --ignore-scripts
+        run: npm ci --ignore-scripts
 
       - name: Lint
-        run: yarn lint
+        run: npm run lint
 
       - name: Build check
-        run: yarn lerna run build:check
+        run: npm run build:check
 
       - name: Build packages
-        run: yarn lerna run build:test
+        run: npm run build:test
 
       - name: Test
-        run: yarn test -i
+        run: npm test -- -i
 
       - name: Test size
-        run: yarn lerna run test:size
+        run: npm run test:size
 
       - name: Test flow
-        run: yarn mobx test:flow
+        run: npm -w mobx run test:flow
 
       - name: Test performance
-        run: yarn mobx test:performance
+        run: npm -w mobx run test:performance

.github/workflows/coveralls.yml

@@ -19,13 +19,13 @@ jobs:
           node-version: 24
 
       - name: Install Dependencies
-        run: yarn --frozen-lockfile --ignore-scripts
+        run: npm ci --ignore-scripts
 
       - name: Build packages
-        run: yarn lerna run build:test
+        run: npm run build:test
 
       # - name: Run Coverage
-      #   run: yarn coverage
+      #   run: npm run coverage
 
       # - name: Upload to coveralls
       #   uses: coverallsapp/github-action@v2.3.6

.github/workflows/release.yml

@@ -31,10 +31,10 @@ jobs:
           registry-url: https://registry.npmjs.org
 
       - name: Install Dependencies
-        run: yarn
+        run: npm ci --ignore-scripts
 
       - name: Build packages
-        run: yarn lerna run build
+        run: npm run build
 
       - name: Create Release Pull Request or Publish to npm
         id: changesets
@@ -44,4 +44,3 @@ jobs:
           publish: npm run release
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-

.gitignore

@@ -13,6 +13,5 @@ dist/
 *.iml
 *.ipr
 *.iws
-yarn-error.log
 build/
 .DS_Store

CONTRIBUTING.md

@@ -33,11 +33,12 @@ For a small bug fix change (less than 20 lines of code changed), feel free to op
 
 #### Getting things running
 
+Use Node.js 24, matching CI. The npm version bundled with Node is sufficient.
+
 ```
 git clone git@github.com:mobxjs/mobx.git
 cd mobx
-yarn install
-yarn lerna run build
-yarn test
+npm install
+npm run build
+npm test
 ```
-