fix: add yarn.lock and use immutable installs for reproducible builds

Author: Mearman

.github/workflows/ci.yml

@@ -38,7 +38,7 @@ jobs:
         run: corepack enable
 
       - name: Install dependencies
-        run: yarn install
+        run: yarn install --immutable
 
       - name: Lint commit messages
         if: github.event_name == 'pull_request'

.github/workflows/release.yml

@@ -30,7 +30,7 @@ jobs:
         run: corepack enable
 
       - name: Install dependencies
-        run: yarn install
+        run: yarn install --immutable
 
       - name: Run tests
         run: yarn test

.github/workflows/semantic-release.yml

@@ -34,7 +34,7 @@ jobs:
         run: corepack enable
 
       - name: Install dependencies
-        run: yarn install
+        run: yarn install --immutable
 
       - name: Run tests
         run: yarn test

.gitignore

@@ -90,4 +90,4 @@ Thumbs.db
 
 # Claude memory files
 .claude/
-CLAUDE.mdyarn.lock
+CLAUDE.md

.yarnrc.yml

@@ -1,4 +1 @@
 nodeLinker: node-modules
-
-# Allow yarn to create lockfile in CI
-enableImmutableInstalls: false