ci: install golangci-lint (Tier-2 quality)

.github/workflows/golangci-lint.yml

@@ -0,0 +1,38 @@
+name: golangci-lint
+
+on:
+  push:
+    branches: [master, main]
+  pull_request:
+    branches: [master, main]
+  schedule:
+    - cron: "23 6 * * 1"
+
+permissions:
+  contents: read
+  pull-requests: read
+
+jobs:
+  lint:
+    name: lint
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          path: common
+      # Sibling checkout (proto) — common itself is the repo under test, so
+      # only proto is fetched as a sibling for the replace directive.
+      - uses: actions/checkout@v4
+        with:
+          repository: InstaNode-dev/proto
+          path: proto
+        continue-on-error: true
+      - uses: actions/setup-go@v5
+        with:
+          go-version-file: common/go.mod
+      - uses: golangci/golangci-lint-action@v8
+        with:
+          version: latest
+          working-directory: common
+          args: --timeout=5m

.golangci.yml

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+# golangci-lint v2 config — start conservative, expand once baseline is clean
+version: "2"
+
+run:
+  timeout: 5m
+  tests: true
+
+linters:
+  # Default linter set is govet+errcheck+ineffassign+staticcheck+unused.
+  # We explicitly add misspell + gocyclo on top. gosimple folded into staticcheck in v2.
+  enable:
+    - errcheck       # checks unchecked errors
+    - govet          # standard vet
+    - ineffassign    # ineffective assignments
+    - staticcheck    # bug detection (subsumes gosimple in v2)
+    - unused         # unused code
+    - misspell       # spelling
+    - gocyclo        # cyclomatic complexity
+  settings:
+    gocyclo:
+      min-complexity: 20
+  exclusions:
+    rules:
+      - path: _test\.go
+        linters:
+          - errcheck
+          - gocyclo
+
+issues:
+  max-issues-per-linter: 0
+  max-same-issues: 0