Add cursor backend and Python constitution tools

[cvalente-il]

Summary

• Add a cursor agent backend that launches the Cursor CLI (agent or cursor-agent) with --workspace, --trust, and --yolo, without Cursor --worktree or headless --print.
• Teach check-backend-dependencies! that cursor is satisfied by either binary.
• Add Python to the shared constitution: pytest, LCOV, and third-party ports of Uncle Bob's tools (mutate4py, crap4py, dry4python) installed into a project-local venv via swarm_tool.sh ensure.

These are community ports, not github.com/unclebob/*4py repos. The constitution names them explicitly so agents do not invent unclebob URLs or homegrown proxies.

Test plan

• clojure.test for swarmforge.script-test and swarmforge.coverage-in-process-test (0 failures)
• swarmforge.handoff-test (0 failures)
• Confirm window coder cursor coder parses and launches when agent or cursor-agent is on PATH
• Confirm Lieutenant cursor starts idle (no initial prompt)
• Confirm swarm_tool.sh ensure crap4py (and mutate4py / dry4python) installs wrappers under .swarmforge/bin