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>

CLAUDE.md

@@ -0,0 +1,41 @@
+# CLAUDE.md — Working Conventions
+
+This file records the conventions Claude must follow throughout this project.
+
+## Plans
+
+Every implementation plan is saved under `docs/plans/` with a filename that
+starts with the **current timestamp in `yyyy-mm-dd-hh-mm` format** followed by
+a short kebab-case description.
+
+Example: `docs/plans/2026-07-01-00-08-go-latency-tool.md`
+
+## Changelog
+
+Every completed feature is appended to `CHANGELOG.md` at the project root with
+a **timestamp** and a one-line description of what was added or changed.
+
+## User Documentation
+
+Every shipped feature must have a corresponding documentation file under
+`docs/usage/`. Each file must include:
+- What the feature does
+- All relevant flags / arguments
+- At least one concrete command-line example with expected output
+
+## Implementation Order
+
+1. Go implementation — developed first, incrementally, with user sign-off
+   between steps.
+2. Python port — begins only after the user approves the Go implementation.
+   Its plan is drafted separately at that time.
+
+## Steps (Go)
+
+| Step | Description |
+|------|-------------|
+| 0    | Scaffold — directory structure, `go.mod`, minimal `main.go` that prints usage |
+| 1    | Simple total latency — single URL, print wall-clock time of the full request |
+| 2    | Per-phase breakdown — DNS, TCP connect, TLS, TTFB, transfer, total via `net/http/httptrace` |
+| 3    | Multiple URLs + sampling — `--count`/`-n` flag, min/avg/max per phase |
+| 4    | JSON output — `--json` flag; text stays default |