feat: auto-detect version via debug.ReadBuildInfo

Replaces the hardcoded Version = "0.1.0" with runtime detection from
Go module build info. 'go install ...@vX.Y.Z' now correctly reports
vX.Y.Z, local source builds show a pseudo-version with commit hash,
and ldflags override still works for custom distributions.

Author: ctm

cmd/root.go

@@ -2,11 +2,33 @@ package cmd
 
 import (
 	"os"
+	"runtime/debug"
 
 	"github.com/spf13/cobra"
 )
 
-var Version = "0.1.0"
+// Version is the ctm version string. It is resolved at runtime from Go's
+// build info when installed via `go install github.com/RandomCodeSpace/ctm@vX.Y.Z`
+// (Go module metadata carries the tag). For local `go build` from source,
+// debug.ReadBuildInfo returns "(devel)" and we fall back to "dev".
+//
+// This variable is also overridable at build time via ldflags for custom
+// distributions:
+//
+//	go build -ldflags "-X github.com/RandomCodeSpace/ctm/cmd.Version=v1.2.3"
+var Version = resolveVersion()
+
+func resolveVersion() string {
+	info, ok := debug.ReadBuildInfo()
+	if !ok {
+		return "dev"
+	}
+	v := info.Main.Version
+	if v == "" || v == "(devel)" {
+		return "dev"
+	}
+	return v
+}
 
 var Verbose bool