chore: initial scaffold for latprobe CLI tool

Sets up project structure, working conventions (CLAUDE.md), README with
the full assignment and roadmap, seeded CHANGELOG, and a buildable Go
scaffold (Step 0) with flag parsing and stub probe types.

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

go/main.go

@@ -0,0 +1,44 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+)
+
+const usageText = `latprobe — measure per-phase HTTP request latency
+
+Usage:
+  latprobe [flags] <url> [url ...]
+
+Flags:
+  -n, --count int   Number of requests per URL (default 1)
+      --json        Output results as JSON instead of text
+  -h, --help        Show this help
+
+Examples:
+  latprobe https://example.com
+  latprobe -n 5 https://example.com https://www.google.com
+  latprobe --json https://example.com | jq .
+`
+
+func main() {
+	count := flag.Int("count", 1, "number of requests per URL")
+	flag.IntVar(count, "n", 1, "number of requests per URL (shorthand)")
+	jsonOut := flag.Bool("json", false, "output results as JSON")
+
+	flag.Usage = func() { fmt.Fprint(os.Stderr, usageText) }
+	flag.Parse()
+
+	urls := flag.Args()
+	if len(urls) == 0 {
+		fmt.Fprint(os.Stderr, usageText)
+		os.Exit(1)
+	}
+
+	// Placeholders — implementations wired in per step.
+	_, _ = count, jsonOut
+
+	fmt.Fprintf(os.Stderr, "latprobe: not yet implemented (scaffold only)\n")
+	os.Exit(1)
+}