fix: add codecov.yml to unblock report processing

Codecov was receiving uploads but never processing them because
ci_passed stayed null — the GitHub App webhook wasn't delivering
CI completion events. Setting wait_for_ci: false and
after_n_builds: 1 tells Codecov to process immediately.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: Fieldnote-Echo

codecov.yml

@@ -0,0 +1,13 @@
+codecov:
+  notify:
+    after_n_builds: 1
+    wait_for_ci: false
+
+coverage:
+  status:
+    project:
+      default:
+        target: auto
+    patch:
+      default:
+        target: auto