feat: add Claude Code project skills for common workflows

[stedrew]

Problem

The project has no .claude/commands/ directory, so Claude Code has no project-specific skills (slash commands) to assist contributors with common tasks. Every contributor has to re-describe routine workflows from scratch in each session.

What are Claude Code skills?

Skills are reusable prompt templates stored as Markdown files under .claude/commands/. They are invoked with /skill-name inside a Claude Code session and expand into a full instruction set, giving Claude the exact context it needs to perform a well-defined task correctly every time.

Proposed skills

/run-sim — Launch a simulation

Prompts Claude to pick the right python -m agentevac.simulation.main invocation: ask for scenario, messaging, metrics, GUI/headless, and produce the ready-to-run command.

/new-scenario — Scaffold a new information regime

Guides Claude through adding a new scenario key to agentevac/agents/scenarios.py (SCENARIO_CHOICES, load_scenario_config, apply_scenario_to_signals, filter_menu_for_scenario) and the matching test stub in tests/test_scenarios.py.

/new-agent-param — Add a new psychological parameter to the agent profile

Walks Claude through the full change surface: agent_state.py profile dict, belief_model.py/departure_model.py usage, spawn defaults in simulation/main.py, and the relevant tests.

/sweep — Run a parameter sweep study

Produces the correct agentevac-study invocation by asking for reference metrics path, sigma/delay/trust ranges, scenario, and output directory.

/replay — Replay a previous run

Resolves the run ID from outputs/ and produces the --run-mode replay --run-id <id> command.

/commit — Conventional commit

Summarises staged changes and produces a correctly formatted Conventional Commits message scoped to this project's modules.

Acceptance criteria

• .claude/commands/ directory created and committed
• Each skill file is concise: context + instructions + example output
• Skills are listed in CLAUDE.md so contributors know they exist