Add GitHub Copilot CLI as a worker backend preset

[anxkhn]

What

Adds a copilot preset so the loop can drive GitHub Copilot CLI as a worker backend, alongside the existing claude_code / codex / opencode / aider presets.

The preset mirrors the existing ones in agentloop/adapters/cli.py:

copilot -p {combined} -s --no-ask-user [--allow-all-tools] [--model <model>]

• -s prints only the final answer (clean stdout to parse, same as the others).
• --no-ask-user keeps the worker autonomous so it never blocks on a question.
• --allow-all-tools is gated behind skip_permissions (the bypass analogue to claude's --dangerously-skip-permissions).
• --model is passed through, same as claude_code.

Wiring

• agentloop/adapters/cli.py: new CliAgent.copilot preset.
• agentloop/mcp_server.py: registered in _CLI_PRESETS, the doctor executable map, backend=auto caller detection (alias + COPILOT_CLI / COPILOT_AGENT_SESSION_ID env hints), and model passthrough.
• examples/run_with_cli_agent.py and README: copilot listed as a selectable backend.

Verification

• uv pip install -e .[dev,mcp]; ruff clean on touched files; full suite 109 passed.
• Added preset shape / skip-permissions / model-passthrough tests.
• Smoke-tested against the real copilot CLI (v1.0.65, authenticated): the preset round-trips a prompt and returns the expected single-word answer.

Note

This repo has no LICENSE file. Please confirm the intended license / contribution terms before merging.

[luckeyfaraday]

Reviewed locally. The license concern in the PR body is resolved now: the repo is clearly MIT-licensed on main and GitHub detects the MIT License widget; follow-up metadata PR #20 is merged.

Local verification:

• python3 -m pytest passes (109 passed)
• GitHub reports this PR as mergeable/clean
• Copilot CLI flags used here match GitHub's documented CLI reference

I could not reproduce the real Copilot CLI smoke test locally because this machine does not have copilot installed, but I do not see a merge blocker from the code or tests.