chore: add codecov coverage tracking

.codecov.yml

@@ -0,0 +1,41 @@
+codecov:
+  require_ci_to_pass: yes
+
+coverage:
+  precision: 2
+  round: down
+  range: "50...100"
+
+  status:
+    project:
+      default:
+        target: auto
+        threshold: 1%
+    patch:
+      default:
+        target: auto
+        threshold: 1%
+
+# Ignore files/directories that tests won't cover
+ignore:
+  - "tests/**"           # Test files
+  - "**/*.test.ts"       # Test files
+  - "**/*.spec.ts"       # Test files
+  - "lib/**"             # Compiled output
+  - "coverage/**"        # Coverage reports
+  - "node_modules/**"    # Dependencies
+
+# Carry forward coverage from previous successful uploads when a flag's
+# report is missing (e.g. a CI test suite failed and skipped uploading).
+# This prevents patch coverage from dropping drastically due to incomplete data.
+flag_management:
+  default_rules:
+    carryforward: true
+
+flags:
+  unit-tests:
+    carryforward: true
+
+comment:
+  layout: "reach,diff,flags,files"
+  behavior: default

.github/workflows/pr-checks.yml

@@ -10,6 +10,9 @@
 name: PR Checks
 
 on:
+  push:
+    branches:
+      - main
   pull_request:
     branches:
       - main
@@ -32,6 +35,9 @@ jobs:
 
   unit-tests:
     runs-on: ubuntu-22.04
+    permissions:
+      contents: read
+      id-token: write
     steps:
       - name: Checkout
         uses: actions/checkout@v3
@@ -50,3 +56,10 @@ jobs:
         run: yarn lint
       - name: Run unit tests
         run: yarn test
+      - name: Upload coverage to Codecov
+        uses: codecov/codecov-action@v6
+        with:
+          use_oidc: true
+          flags: unit-tests
+          files: coverage/lcov.info
+          fail_ci_if_error: false