Restore config loading, keep exported Version, keep cgo off

Bring back the in-progress viper and go-homedir configuration loading
from the original root command as a persistent pre-run on the root
command, with a --config flag and a config line in sutil info. Restore
the exported main.Version with a nolint directive instead of renaming
it. Export CGO_ENABLED=0 from the Makefile, drop -race from make test,
and remove the C toolchain from the Docker builder stage.

Makefile

@@ -9,7 +9,7 @@
 
 BINARY := sutil
 VERSION := $(shell git describe --always --dirty 2>/dev/null || echo dev)
-GOLDFLAGS := -X main.version=$(VERSION)
+GOLDFLAGS := -X main.Version=$(VERSION)
 GO_DIRS := cmd internal pkg
 
 # golangci/golangci-lint:v2.12.2, 2026-05-06
@@ -25,6 +25,10 @@ MARKDOWN_GLOB := '**/*.md'
 
 all: build
 
+# cgo stays off everywhere: builds are static and the tests do not use
+# -race, which would require a C toolchain.
+export CGO_ENABLED := 0
+
 # Build the sutil binary in the repo root with the git version embedded.
 build:
 	go build -trimpath -ldflags "$(GOLDFLAGS)" -o $(BINARY) ./cmd/$(BINARY)
@@ -36,9 +40,9 @@ install:
 # Run the tests quietly; on failure rerun verbosely for diagnostics and
 # still fail.
 test:
-	@go test -timeout 30s -race -cover ./... || \
+	@go test -timeout 30s -cover ./... || \
 		{ echo "--- Rerunning with -v for details ---"; \
-		  go test -timeout 30s -race -v ./...; exit 1; }
+		  go test -timeout 30s -v ./...; exit 1; }
 
 # Lint with the pinned golangci-lint image when docker is available so local
 # results match CI exactly. Inside the Docker build (where there is no