chore: wire hxprobe into root project (Makefile, CLAUDE.md, .gitignore)

Makefile: add hx-* targets (deps, run, lint, fmt, test, test-integration,
check, clean) that delegate into hxprobe/ via uv; fold hx-test and hx-check
into the umbrella test/check/clean targets; add HX_DIR variable and a note
that hxprobe is intentionally standalone (no cross-imports from python/).

CLAUDE.md: add "Implementation Summaries" convention — after each feature,
save a summary under docs/summaries/ with the same timestamp+slug naming as
plans. Add note about copying plan-mode scratch files into docs/plans/ before
starting implementation.

.gitignore: add *.egg-info/, .pytest_cache/, .ruff_cache/ for the hxprobe
uv+ruff+pytest toolchain.

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

Makefile

@@ -1,9 +1,14 @@
-GO_DIR  := go
-PY_DIR  := python
-BINARY  := latprobe
-PYTHON  := python3.14
-ARGS    ?=
-SITES   ?= $(PY_DIR)/sites.txt
+GO_DIR   := go
+PY_DIR   := python
+BINARY   := latprobe
+PYTHON   := python3.14
+ARGS     ?=
+SITES    ?= $(PY_DIR)/sites.txt
+
+# hxprobe is a fully standalone project (own pyproject.toml, own uv-managed
+# venv/lockfile) — it imports nothing from python/latprobe, and could be
+# `cp -r`'d into its own repo as-is.
+HX_DIR := hxprobe
 
 .DEFAULT_GOAL := help
 
@@ -24,10 +29,10 @@ all: check build ## Run checks then build
 build: go-build ## Build binary (delegates to go-build)
 
 .PHONY: test
-test: go-test py-test ## Run all tests (Go + Python)
+test: go-test py-test hx-test ## Run all tests (Go + Python + hxprobe)
 
 .PHONY: check
-check: go-check py-check ## Run fmt + vet + test gate (Go + Python)
+check: go-check py-check hx-check ## Run fmt + vet + test gate (Go + Python + hxprobe)
 
 .PHONY: fmt
 fmt: go-fmt ## Format source code (delegates to go-fmt)
@@ -36,7 +41,7 @@ fmt: go-fmt ## Format source code (delegates to go-fmt)
 vet: go-vet ## Run go vet (delegates to go-vet)
 
 .PHONY: clean
-clean: go-clean py-clean ## Remove build and coverage artifacts
+clean: go-clean py-clean hx-clean ## Remove build and coverage artifacts
 
 # ── Go targets ────────────────────────────────────────────────────────────────
 
@@ -126,3 +131,39 @@ py-check: py-test ## py: run Python test gate (hermetic only)
 py-clean: ## py: remove Python bytecode and __pycache__ dirs
 	@find $(PY_DIR) -type d -name '__pycache__' -exec rm -rf {} + 2>/dev/null; \
 	find $(PY_DIR) -name '*.pyc' -delete 2>/dev/null; true
+
+# ── hxprobe (standalone httpx-based probe; own pyproject.toml/uv.lock, no
+# imports from python/latprobe — see hxprobe/pyproject.toml) ─────────────────
+
+.PHONY: hx-deps
+hx-deps: ## hx: sync hxprobe's uv-managed environment from its lockfile; idempotent
+	cd $(HX_DIR) && uv sync
+
+.PHONY: hx-run
+hx-run: hx-deps ## hx: run hxprobe (pass flags via ARGS="…")
+	cd $(HX_DIR) && uv run python -m hxprobe $(ARGS)
+
+.PHONY: hx-lint
+hx-lint: hx-deps ## hx: lint hxprobe with ruff
+	cd $(HX_DIR) && uv run ruff check .
+
+.PHONY: hx-fmt
+hx-fmt: hx-deps ## hx: format hxprobe with ruff
+	cd $(HX_DIR) && uv run ruff format .
+
+.PHONY: hx-test
+hx-test: hx-deps ## hx: run hxprobe unit tests (hermetic)
+	cd $(HX_DIR) && uv run pytest tests -m "not integration" -v $(ARGS)
+
+.PHONY: hx-test-integration
+hx-test-integration: hx-deps ## hx: run hxprobe integration tests against live internet services (HTTP/2, redirects)
+	cd $(HX_DIR) && uv run pytest tests -m integration -v $(ARGS)
+
+.PHONY: hx-check
+hx-check: hx-lint hx-test ## hx: run hxprobe test gate (lint + hermetic tests)
+
+.PHONY: hx-clean
+hx-clean: ## hx: remove hxprobe bytecode, caches, and egg-info
+	@find $(HX_DIR) -type d -name '__pycache__' -exec rm -rf {} + 2>/dev/null; \
+	find $(HX_DIR) -name '*.pyc' -delete 2>/dev/null; \
+	rm -rf $(HX_DIR)/*.egg-info $(HX_DIR)/.pytest_cache $(HX_DIR)/.ruff_cache; true