ci: run full test suite on main, critical-only on PRs (#25)

- PRs: Run tests/critical/ only (fast CI feedback, ~1-2 min)
- Main push: Run tests/ full suite (accurate coverage, ~10 min)
- Add codecov.yml with carryforward flags configuration
- Use dynamic flags: full-python-X.Y vs critical-python-X.Y

Coverage improves from ~52% (critical) to ~77% (full) on main.

Author: 27Bslash6

.github/workflows/ci.yml

@@ -166,7 +166,8 @@ jobs:
       run: |
         uv sync --group dev
 
-    - name: Run critical tests with coverage
+    - name: Run critical tests (PRs)
+      if: github.event_name == 'pull_request'
       env:
         REDIS_URL: redis://localhost:6379
       run: |
@@ -177,14 +178,26 @@ jobs:
           --junitxml=junit.xml \
           -o junit_family=legacy
 
+    - name: Run full test suite (main)
+      if: github.event_name == 'push'
+      env:
+        REDIS_URL: redis://localhost:6379
+      run: |
+        uv run pytest tests/ -m "not slow" \
+          --cov=src/cachekit \
+          --cov-report=xml \
+          --cov-report=term \
+          --junitxml=junit.xml \
+          -o junit_family=legacy
+
     - name: Upload coverage to Codecov
       if: ${{ !cancelled() }}
       uses: codecov/codecov-action@v5
       with:
         files: ./coverage.xml
         use_oidc: true
         fail_ci_if_error: false
-        flags: python-${{ matrix.python-version }}
+        flags: ${{ github.event_name == 'push' && 'full' || 'critical' }}-python-${{ matrix.python-version }}
 
     - name: Upload test results to Codecov
       if: ${{ !cancelled() }}
@@ -193,7 +206,7 @@ jobs:
         files: ./junit.xml
         report_type: test_results
         use_oidc: true
-        flags: python-${{ matrix.python-version }}
+        flags: ${{ github.event_name == 'push' && 'full' || 'critical' }}-python-${{ matrix.python-version }}
         fail_ci_if_error: false
 
   # Markdown documentation tests

codecov.yml

@@ -0,0 +1,39 @@
+# Codecov Configuration
+# https://docs.codecov.com/docs/codecovyml-reference
+
+coverage:
+  status:
+    project:
+      default:
+        target: auto
+        threshold: 2%  # Allow 2% coverage drop without failing
+    patch:
+      default:
+        target: 80%  # New code should have 80% coverage
+
+# Flag configuration for PR vs main coverage strategy
+flag_management:
+  default_rules:
+    carryforward: true  # Carry forward coverage from previous uploads
+    statuses:
+      - type: project
+      - type: patch
+
+  individual_flags:
+    # Full test suite (main branch only)
+    - name: full-python-3.12
+      carryforward: true
+      paths:
+        - src/cachekit/
+
+    # Critical tests (PRs) - carryforward from full coverage
+    - name: critical-python-3.12
+      carryforward: true
+      carryforward_mode: labels
+      paths:
+        - src/cachekit/
+
+comment:
+  layout: "header, diff, flags, components"
+  behavior: default
+  require_changes: true  # Only comment if coverage changed