phase 0 + 1: repo bones and ETF codec

Repo scaffolding (LICENSE, Makefile, pyproject.toml, README) matching
unfeed conventions. Flat package layout, ruff config, Unlicense.

ETF codec covers the subset needed for gen_call against an Elixir node:
small/int/big_int, atom_utf8 (legacy atom_ext on decode), binary, nil,
list, small/large tuple, new_pid, newer_reference. Booleans round-trip
as atoms true/false; Python None as atom nil; str encodes to utf-8
binary to match Elixir convention.

Golden vectors were generated from real Erlang term_to_binary/1 output
(generator script at docs/etf_vectors.erl). Decode tests verify wire
compatibility; round-trip tests verify encoder consistency.

make all green: 58 passed, lint clean.

Next phases tracked in docs/ROADMAP.md (EPMD, handshake, channel,
gen_call, TLS, unfeed integration).

Makefile

@@ -0,0 +1,42 @@
+VENV_DIR = $(shell pwd)/.venv
+PYTHON   = $(VENV_DIR)/bin/python
+PIP      = $(VENV_DIR)/bin/pip
+PYTEST   = $(VENV_DIR)/bin/pytest
+RUFF     = $(VENV_DIR)/bin/ruff
+
+.DEFAULT_GOAL := all
+.PHONY: all bootstrap venv install test lint format clean help
+
+all: bootstrap test lint
+
+help:
+	@echo "erldistpy targets"
+	@echo "  make bootstrap   - create venv, install editable + dev deps"
+	@echo "  make test        - run pytest"
+	@echo "  make lint        - ruff check"
+	@echo "  make format      - ruff format"
+	@echo "  make clean       - drop venv + caches"
+
+venv:
+	test -d $(VENV_DIR) || python3 -m venv $(VENV_DIR)
+	$(PIP) install --upgrade pip wheel setuptools
+
+bootstrap: venv
+	$(PIP) install -e ".[dev]"
+
+install: bootstrap
+
+test:
+	$(PYTEST) -v
+
+lint:
+	$(RUFF) check erldistpy tests
+
+format:
+	$(RUFF) format erldistpy tests
+
+clean:
+	rm -rf $(VENV_DIR)
+	rm -rf .pytest_cache .ruff_cache
+	rm -rf build dist *.egg-info
+	find . -type d -name __pycache__ -exec rm -rf {} +