fix(ci): remove jest coverageThreshold — tighten codecov.yml to 80% hard floor

In the split CI matrix (unit / integration / e2e), each job only loads its
slice of collectCoverageFrom paths, so a global Jest threshold always fails
(reports 61% instead of 80%). The correct enforcement layer is Codecov, which
merges unit + integration flags server-side before applying the gate.

Changes:
- jest.config.js: remove coverageThreshold; add explanatory comment (efd7bbc rationale)
- codecov.yml: harden project target from `auto` to 80% hard floor to prevent
  long-term coverage decay; patch stays `auto` (new code matches local module baseline)

Author: PierreBrisorgueil

codecov.yml

@@ -2,15 +2,15 @@ coverage:
   status:
     project:
       default:
-        target: auto
-        threshold: 0.5%
+        target: 80%        # hard floor — prevents long-term coverage decay (auto allows drift)
+        threshold: 0.5%    # allow ≤0.5% transient drop within the 80% floor
         flags:
           - unit
           - integration
     patch:
       default:
-        target: auto
-        threshold: 0%
+        target: auto       # new code must match local module baseline (not abstract 80%)
+        threshold: 0%      # no tolerance on new code
         flags:
           - unit
           - integration

jest.config.js

@@ -67,15 +67,13 @@ export default {
   // A list of reporter names that Jest uses when writing coverage reports
   coverageReporters: ['json', 'lcov', 'clover', 'text'],
 
-  // Codecov delta gating (codecov.yml) stays as a second layer; both gates are active.
-  coverageThreshold: {
-    global: {
-      statements: 80,
-      branches: 65,
-      functions: 80,
-      lines: 80,
-    },
-  },
+  // coverageThreshold removed — coverage gating moved to Codecov status checks.
+  // In the split test matrix (unit / integration / e2e), each CI job only sees
+  // its slice of `collectCoverageFrom`, so a global Jest threshold would fail
+  // in every job (61% instead of 80% because only one suite's paths are loaded).
+  // Codecov merges the unit + integration flags server-side and applies an 80%
+  // project floor there (see codecov.yml status.project). This was the design
+  // since efd7bbc7 (2026-05-01) — not a loosening of coverage enforcement.
 
   // Make calling deprecated APIs throw helpful error messages
   // errorOnDeprecated: false,