Add per-directory codecov coverage targets

The osapi/ package contains ~194k lines of generated code covering
every API in the OpenSearch spec. Coverage sits at ~25% because many
generated APIs target plugin-specific endpoints (ISM, anomaly
detection, k-NN, security, notifications) that require plugins not
present in the CI cluster.

Unit-level roundtrip tests exercise request construction and dispatch
for all 167 APIs, but full response parsing coverage requires
integration tests against a cluster with the relevant plugins enabled.
Expanding the CI cluster configuration and adding plugin-aware
integration tests would raise this target over time.

Component-level targets:

  core (transport, utils, signer):  80%  - mature, hand-written code
  internal/path:                    95%  - small, fully testable
  osapi:                            25%  - limited by CI plugin set
  opensearchapi (legacy):           14%  - frozen, being replaced

Signed-off-by: Sean Chittenden <sean.chittenden@crowdstrike.com>

Author: sean-

.codecov.yml

@@ -11,5 +11,29 @@ coverage:
   status:
     project:
       default:
-        threshold: 5%  # allow 5% coverage decrease
+        target: auto
+        threshold: 5%
+      core:
+        paths:
+          - "opensearch*.go"
+          - "opensearchtransport/"
+          - "opensearchutil/"
+          - "signer/"
+        target: 80%
+        threshold: 2%
+      path:
+        paths:
+          - "internal/path/"
+        target: 95%
+        threshold: 2%
+      osapi:
+        paths:
+          - "osapi/"
+        target: 25%
+        threshold: 5%
+      opensearchapi:
+        paths:
+          - "opensearchapi/"
+        target: 14%
+        threshold: 2%
     patch: off