feat(install) + docs + chore(workplan): complete T03 for CYA-WP-0004 — Makefile, optional deps, and improved dev-head installation docs

Makefile

@@ -0,0 +1,30 @@
+# Simple developer Makefile for can-you-assist
+# Focus: easy dev-head install and common tasks
+
+.PHONY: dev-install install test clean dist
+
+# Install the package in editable mode from the current source
+# This is the recommended way to work on the latest code
+dev-install:
+	pip install -e ".[dev]"
+
+# Standard install (for comparison / released packages later)
+install:
+	pip install .
+
+# Run the test suite
+test:
+	python3 -m pytest tests/ -q
+
+# Clean build artifacts
+clean:
+	rm -rf build/ dist/ *.egg-info/ src/cya/_version.py
+	find . -type d -name __pycache__ -exec rm -rf {} + 2>/dev/null || true
+
+# Build distribution packages (sdist + wheel)
+dist: clean
+	python -m build
+
+# Show current version (useful after setuptools_scm changes)
+version:
+	python3 -c "import cya; print(cya.__version__)"