feat(go): step 1 — total wall-clock latency per URL

probe.Measure performs an HTTP GET and records total elapsed time from
request start to body fully read. main.go prints URL, status code, and
total for each positional URL argument, exiting 1 on any failure.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

go/main.go

@@ -4,6 +4,9 @@ import (
 	"flag"
 	"fmt"
 	"os"
+	"time"
+
+	"latprobe/internal/probe"
 )
 
 const usageText = `latprobe — measure per-phase HTTP request latency
@@ -36,9 +39,22 @@ func main() {
 		os.Exit(1)
 	}
 
-	// Placeholders — implementations wired in per step.
-	_, _ = count, jsonOut
+	// --json and -n are parsed but not yet functional (wired in Steps 3–4).
+	_ = jsonOut
+	_ = count
 
-	fmt.Fprintf(os.Stderr, "latprobe: not yet implemented (scaffold only)\n")
-	os.Exit(1)
+	failed := false
+	for _, url := range urls {
+		r := probe.Measure(url)
+		if r.Err != nil {
+			fmt.Fprintf(os.Stderr, "error %s: %v\n", url, r.Err)
+			failed = true
+			continue
+		}
+		fmt.Printf("%-45s  %d  %v\n", r.URL, r.StatusCode, r.Total.Duration.Round(time.Millisecond))
+	}
+
+	if failed {
+		os.Exit(1)
+	}
 }