fix(ci): don't capture tool-download noise as a formatting diff

The gofumpt check merged stderr into the diff variable, so 'go:
downloading ...' lines made it always fail. Move tool installation into
its own step (adding GOPATH/bin to PATH) and capture only stdout.

.gitea/workflows/release.yml

@@ -23,9 +23,16 @@ jobs:
       - name: go vet
         run: go vet ./...
 
+      - name: Install lint tools
+        run: |
+          go install github.com/golangci/golangci-lint/v2/cmd/golangci-lint@latest
+          go install honnef.co/go/tools/cmd/staticcheck@latest
+          go install golang.org/x/vuln/cmd/govulncheck@latest
+          echo "$(go env GOPATH)/bin" >> "$GITHUB_PATH"
+
       - name: gofumpt (golangci-lint fmt)
         run: |
-          diff=$(go run github.com/golangci/golangci-lint/v2/cmd/golangci-lint@latest fmt --diff 2>&1)
+          diff=$(golangci-lint fmt --diff)
           if [ -n "$diff" ]; then
             echo "$diff"
             echo "Formatting issues found. Run: make fmt"
@@ -33,10 +40,10 @@ jobs:
           fi
 
       - name: staticcheck
-        run: go run honnef.co/go/tools/cmd/staticcheck@latest ./...
+        run: staticcheck ./...
 
       - name: govulncheck
-        run: go run golang.org/x/vuln/cmd/govulncheck@latest ./...
+        run: govulncheck ./...
 
       - name: Test
         run: go test ./...

Makefile

@@ -58,7 +58,7 @@ fmt: ## Format code (gofumpt + goimports via golangci-lint)
 
 fmt-check: ## Check formatting (gofumpt + goimports via golangci-lint)
 	@echo "Checking formatting..."
-	@diff=$$($(GOLANGCI_LINT) fmt --diff --config=.golangci.json 2>&1); \
+	@diff=$$($(GOLANGCI_LINT) fmt --diff --config=.golangci.json); \
 	if [ -n "$$diff" ]; then echo "$$diff"; echo "Run: make fmt"; exit 1; fi
 
 staticcheck: ## Run staticcheck