test: add comprehensive unit tests, fixtures, and golangci-lint config

.golangci.yml

@@ -0,0 +1,57 @@
+run:
+  timeout: 5m
+  go: "1.26"
+
+linters:
+  enable:
+    - errcheck
+    - gosimple
+    - govet
+    - ineffassign
+    - staticcheck
+    - unused
+    - gofmt
+    - gosec
+    - revive
+    - misspell
+
+linters-settings:
+  gosec:
+    excludes:
+      - G104 # Audit errors not checked (errcheck covers this)
+  revive:
+    rules:
+      - name: blank-imports
+        disabled: false
+      - name: context-as-argument
+        disabled: false
+      - name: dot-imports
+        disabled: false
+      - name: error-naming
+        disabled: false
+      - name: error-strings
+        disabled: false
+      - name: errorf
+        disabled: false
+      - name: increment-decrement
+        disabled: false
+      - name: indent-error-flow
+        disabled: false
+      - name: range
+        disabled: false
+      - name: receiver-naming
+        disabled: false
+      - name: time-naming
+        disabled: false
+      - name: unexported-return
+        disabled: false
+      - name: var-declaration
+        disabled: false
+
+issues:
+  exclude-use-default: true
+  exclude-rules:
+    - path: _test\.go
+      linters:
+        - gosec
+        - errcheck

Makefile

@@ -10,7 +10,14 @@ fmt:
 	@go fmt ./...
 
 lint:
-	@golangci-lint run
+	@if command -v golangci-lint >/dev/null 2>&1; then \
+		golangci-lint run; \
+	elif [ -x "$$(go env GOPATH)/bin/golangci-lint" ]; then \
+		"$$(go env GOPATH)/bin/golangci-lint" run; \
+	else \
+		echo "golangci-lint not found (run 'make dev-setup')"; \
+		exit 1; \
+	fi
 
 cfn-lint: ## Lint CloudFormation templates (requires cfn-lint)
 	@echo "==> Linting CloudFormation templates"