fix(ci): upgrade golangci-lint v1.62.2 to v2.11.4 for Go 1.25 support

The old v1 binary was built with Go 1.23 and rejected Go 1.25 targets.
Migrated .golangci.yml to v2 format: added version field, moved
linters-settings under linters.settings, removed deprecated linters
(structcheck/deadcode/varcheck), merged gosimple into staticcheck.

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

.github/workflows/ci.yml

@@ -33,7 +33,7 @@ jobs:
 
       - name: Install golangci-lint
         run: |
-          curl -sSfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | sh -s -- -b $(go env GOPATH)/bin v1.62.2
+          curl -sSfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | sh -s -- -b $(go env GOPATH)/bin v2.11.4
 
       - name: Run golangci-lint
         run: golangci-lint run ./... --timeout 5m

.golangci.yml

@@ -1,36 +1,32 @@
+version: "2"
+
 run:
   timeout: 5m
 
 linters:
+  default: none
   enable:
     - errcheck
     - govet
     - staticcheck
     - unused
-    - gosimple
     - ineffassign
     - typecheck
     - gocritic
     - gosec
     - bodyclose
     - noctx
-  disable:
-    - structcheck  # deprecated
-    - deadcode     # deprecated
-    - varcheck     # deprecated
-
-linters-settings:
-  errcheck:
-    check-type-assertions: true
-  gocritic:
-    enabled-tags:
-      - diagnostic
-      - performance
-  gosec:
-    excludes:
-      - G104  # Audit errors not checked (we have intentional fire-and-forget patterns)
-      - G304  # File inclusion via variable (needed for config-driven file paths)
-
-issues:
-  max-issues-per-linter: 50
-  max-same-issues: 5
+  settings:
+    errcheck:
+      check-type-assertions: true
+    gocritic:
+      enabled-tags:
+        - diagnostic
+        - performance
+    gosec:
+      excludes:
+        - G104  # Audit errors not checked (we have intentional fire-and-forget patterns)
+        - G304  # File inclusion via variable (needed for config-driven file paths)
+  exclusions:
+    max-issues-per-linter: 50
+    max-same-issues: 5