Revert to free ubuntu-latest runners instead of paid 4-core runners

Using standard ubuntu-latest (2-core) runners for light jobs to avoid
additional costs beyond GitHub Team plan. Heavy jobs still use self-hosted.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -15,7 +15,7 @@ jobs:
   # Lint job - fast and independent
   lint:
     name: Lint & Format Check
-    runs-on: ubuntu-latest-4-cores
+    runs-on: ubuntu-latest
     
     steps:
     - name: Checkout code
@@ -40,7 +40,7 @@ jobs:
   # Unit tests - fastest test suite
   test-unit:
     name: Unit Tests
-    runs-on: ubuntu-latest-4-cores
+    runs-on: ubuntu-latest
     
     steps:
     - name: Checkout code
@@ -67,7 +67,7 @@ jobs:
   # Integration tests - moderate complexity
   test-integration:
     name: Integration Tests
-    runs-on: ubuntu-latest-4-cores
+    runs-on: ubuntu-latest
     
     steps:
     - name: Checkout code
@@ -121,7 +121,7 @@ jobs:
   # Coverage generation - depends on unit tests
   coverage:
     name: Test Coverage
-    runs-on: ubuntu-latest-4-cores
+    runs-on: ubuntu-latest
     needs: [test-unit]
     
     steps:

.github/workflows/deploy.yml

@@ -21,7 +21,7 @@ jobs:
   
   test:
     name: Run Tests
-    runs-on: ubuntu-latest-4-cores
+    runs-on: ubuntu-latest
     strategy:
       matrix:
         node-version: [18.x, 20.x]
@@ -107,7 +107,7 @@ jobs:
 
   security-scan:
     name: Security Scanning
-    runs-on: ubuntu-latest-4-cores
+    runs-on: ubuntu-latest
     needs: build
     if: github.event_name != 'pull_request'