fix(ci): align golangci-lint config with v2.6 schema (remove 'issues.exclude')

.golangci.yml

@@ -20,10 +20,5 @@ linters:
 issues:
   max-issues-per-linter: 0
   max-same-issues: 0
-  exclude:
+  # Note: exclusion rules moved in v2 config; keep minimal allowed keys
-    # Exclude test files from some checks
-    - path: _test\.go
-      linters:
-        - errcheck
-        - gosec