ci: make coverage ratchet lossless

.github/workflows/ci.yml

@@ -94,6 +94,7 @@ jobs:
           name: vitest-coverage-unit-${{ matrix.shard }}
           path: .vitest-reports/unit-${{ matrix.shard }}.blob
           include-hidden-files: true
+          if-no-files-found: error
           retention-days: 1
 
   integration:
@@ -122,6 +123,7 @@ jobs:
           name: vitest-coverage-integration-${{ matrix.shard }}
           path: .vitest-reports/integration-${{ matrix.shard }}.blob
           include-hidden-files: true
+          if-no-files-found: error
           retention-days: 1
 
   coverage:
@@ -142,6 +144,13 @@ jobs:
           pattern: vitest-coverage-*
           path: .vitest-reports
           merge-multiple: true
+      - name: Verify every coverage shard is present
+        run: |
+          test -f .vitest-reports/unit-1.blob
+          test -f .vitest-reports/unit-2.blob
+          test -f .vitest-reports/integration-1.blob
+          test -f .vitest-reports/integration-2.blob
+          test "$(find .vitest-reports -type f -name '*.blob' | wc -l)" -eq 4
       - name: Merge coverage and enforce thresholds
         env:
           COVERAGE_ENFORCE: '1'

vitest.config.ts

@@ -39,13 +39,13 @@ const coverageConfig = {
 const coverageGate =
   process.env.COVERAGE_ENFORCE === '1'
     ? {
-        // Integer floors of the merged CI shard baseline. Keep this as a ratchet:
-        // production growth must preserve or improve the repository-wide result.
+        // Lock the merged CI baseline by maximum uncovered items. Unlike rounded
+        // percentages, negative thresholds cannot hide a small coverage regression.
         thresholds: {
-          statements: 86,
-          branches: 75,
-          functions: 66,
-          lines: 94,
+          statements: -2099,
+          branches: -2869,
+          functions: -1924,
+          lines: -717,
         },
       }
     : {}