fix(ci): migrate golangci-lint config to v2 format

v2.x is required by golangci-lint-action@v9. Key changes:
- linters.default: none replaces disable-all
- linters.settings + formatters.settings replace linters-settings
- linters.exclusions.rules replaces issues.exclude-rules
- gosimple merged into staticcheck
- run.timeout removed (no longer a config field in v2)

Author: DeliciousBuding

.github/workflows/ci.yml

@@ -39,4 +39,4 @@ jobs:
           go-version-file: go.mod
       - uses: golangci/golangci-lint-action@v9
         with:
-          version: v1.64
+          version: latest

.golangci.yml

@@ -1,62 +1,63 @@
+version: "2"
+
 run:
-  timeout: 3m
   tests: true
-  go: "1.24"
 
 linters:
-  disable-all: true
+  default: none
   enable:
     - errcheck
-    - gosimple
     - govet
     - ineffassign
     - staticcheck
     - unused
     - misspell
     - unconvert
     - revive
+  settings:
+    errcheck:
+      check-type-assertions: false
+      exclude-functions:
+        - encoding/json.Unmarshal
+        - encoding/json.Marshal
+        - (*encoding/json.Encoder).Encode
+        - fmt.Fprintln
+        - fmt.Fprintf
+        - fmt.Println
+        - fmt.Printf
+    revive:
+      rules:
+        - name: blank-imports
+        - name: context-as-argument
+        - name: error-return
+        - name: error-strings
+        - name: error-naming
+        - name: exported
+          arguments: ["disableStutteringCheck"]
+        - name: increment-decrement
+        - name: var-declaration
+        - name: range
+        - name: receiver-naming
+        - name: time-naming
+        - name: unexported-return
+        - name: indent-error-flow
+        - name: errorf
+        - name: empty-block
+        - name: superfluous-else
+        - name: unused-parameter
+  exclusions:
+    rules:
+      - path: _test\.go
+        linters:
+          - errcheck
+          - revive
+          - unused
+
+formatters:
+  enable:
     - gofmt
     - goimports
 
-linters-settings:
-  errcheck:
-    check-type-assertions: false
-    exclude-functions:
-      - encoding/json.Unmarshal
-      - encoding/json.Marshal
-      - (*encoding/json.Encoder).Encode
-      - fmt.Fprintln
-      - fmt.Fprintf
-      - fmt.Println
-      - fmt.Printf
-
-  revive:
-    rules:
-      - name: blank-imports
-      - name: context-as-argument
-      - name: error-return
-      - name: error-strings
-      - name: error-naming
-      - name: exported
-        arguments: ["disableStutteringCheck"]
-      - name: increment-decrement
-      - name: var-declaration
-      - name: range
-      - name: receiver-naming
-      - name: time-naming
-      - name: unexported-return
-      - name: indent-error-flow
-      - name: errorf
-      - name: empty-block
-      - name: superfluous-else
-      - name: unused-parameter
-
 issues:
-  exclude-rules:
-    - path: _test\.go
-      linters:
-        - errcheck
-        - revive
-        - unused
   max-issues-per-linter: 0
   max-same-issues: 0