Align CONTRIBUTING.md with the current development setup

## Summary

`CONTRIBUTING.md` still documents an older local-development path. It lists Python 3.11+, Node 20+, npm commands, and `orbit-agent-console`, while the current repository uses Python 3.13+, Node 24+, pnpm, and the `orbit` command.

This is a documentation-only contribution with no product-code changes required.

## Scope

- Update the required Python and Node.js versions to match the project configuration and README.
- Replace obsolete npm commands with the current pnpm commands.
- Replace the obsolete packaged-app command with the current `orbit run` command.
- Keep the development, pre-commit, and release instructions internally consistent.

## Acceptance criteria

- The development instructions agree with `README.md`, `pyproject.toml`, and `package.json`.
- No reference to the removed `orbit-agent-console` command remains.
- Commands are copyable and use the repository's declared package manager.
- No production source code changes are needed.

## Helpful files

- `CONTRIBUTING.md`
- `README.md`
- `pyproject.toml`
- `package.json`

Questions are welcome—please leave a comment if any command or version requirement is unclear.