feat(hxprobe): httpx-based HTTP probe — full standalone package

Third Python implementation in the latency-tool progression.
Mirrors latprobe's feature set but replaces raw sockets with httpx,
gaining HTTP/2 support and redirect following.

Package layout (hxprobe/hxprobe/):
- probe.py: asyncio + httpx.AsyncClient with a _TimingStream transport
  wrapper that captures DNS/connect/TLS/TTFB/transfer phase timings via
  httpx event hooks (get_connection_stats, request_started, etc.).
  VerboseDetail captures resolved IP, TLS version/cipher/bits, cert CN/
  expiry/issuer (from httpx's SSLObject), and response headers.
  Options: timeout, verbose, follow_redirects, http2
- aggregate.py: summarize() → per-phase min/avg/max (same schema as latprobe)
- cli.py: run(args,stdout,stderr)->int; argparse with redirect_stdout/
  redirect_stderr + SystemExit catch; -n/--count, -c/--concurrency,
  --timeout, --fail, --json, -v/--verbose, --no-follow-redirects,
  --no-http2, -f/--file (URL list from file, mutually exclusive with args);
  multi-URL summary footer (tally + exit label) when len(urls) > 1;
  worst-exit-code logic mirrors Go/latprobe; JSON output is bare array
- duration.py: same parse_duration() as latprobe
- Exit codes: 0 ok, 1 usage, 2 dns, 3 connect, 4 timeout, 5 tls, 6 http≥400

Tests (hxprobe/tests/):
- test_probe.py: 18 hermetic tests using anyio + in-process ASGI servers
- test_cli.py: 36 hermetic tests (success, failures, JSON, verbose, -f flag,
  run-summary footer, worst-code accumulation)
- test_integration.py: pytest-marked @integration (excluded from hx-test)

Toolchain: uv + ruff + pytest; pyproject.toml with [dependency-groups];
hxprobe/Makefile standalone (help, deps, run, lint, fmt, test,
test-integration, check, clean); .python-version pins 3.14
Configs: 8 fixture files mirroring python/configs/ (all-ok through mixed)
USAGE.md: 16 runnable examples with real captured output

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

hxprobe/Makefile

@@ -0,0 +1,55 @@
+# hxprobe — standalone Makefile. Requires uv (https://docs.astral.sh/uv/).
+#
+# This project is fully self-contained (own pyproject.toml, own uv.lock) and
+# this Makefile works the same whether run from inside a parent monorepo or
+# after `cp -r`'ing hxprobe/ into its own repo. It does not depend on, and is
+# not depended on by, the parent repo's root Makefile — the two are kept
+# independent on purpose so a change to one can't break the other.
+
+PYTHON ?= python3.14
+ARGS   ?=
+
+.DEFAULT_GOAL := help
+
+# ── help ──────────────────────────────────────────────────────────────────────
+
+.PHONY: help
+help: ## Show this help
+	@grep -E '^[a-zA-Z_-]+:.*##' $(MAKEFILE_LIST) \
+		| awk 'BEGIN {FS = ":.*##"}; {printf "  \033[36m%-20s\033[0m %s\n", $$1, $$2}' \
+		| sort
+
+# ── targets ───────────────────────────────────────────────────────────────────
+
+.PHONY: deps
+deps: ## sync the venv from uv.lock; idempotent
+	uv sync
+
+.PHONY: run
+run: deps ## run hxprobe (pass flags via ARGS="…")
+	uv run $(PYTHON) -m hxprobe $(ARGS)
+
+.PHONY: lint
+lint: deps ## lint with ruff
+	uv run ruff check .
+
+.PHONY: fmt
+fmt: deps ## format with ruff
+	uv run ruff format .
+
+.PHONY: test
+test: deps ## run hermetic unit tests
+	uv run pytest tests -m "not integration" -v $(ARGS)
+
+.PHONY: test-integration
+test-integration: deps ## run integration tests against live internet services (HTTP/2, redirects)
+	uv run pytest tests -m integration -v $(ARGS)
+
+.PHONY: check
+check: lint test ## run the full gate: lint + hermetic tests
+
+.PHONY: clean
+clean: ## remove bytecode, caches, and egg-info
+	@find . -type d -name '__pycache__' -exec rm -rf {} + 2>/dev/null; \
+	find . -name '*.pyc' -delete 2>/dev/null; \
+	rm -rf *.egg-info .pytest_cache .ruff_cache; true