[FEATURE]: add docker-based bun workflow for contributors

• I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

Add an officially supported Docker-based Bun workflow for contributors who cannot run Bun natively in their environment.

Proposed scope:

• Add a helper script (for example script/bun-docker.sh) that runs Bun commands inside a pinned oven/bun image.
• Ensure native dependency installs work by including minimal build dependencies in the container image (python3, make, g++, git).
• Document usage in CONTRIBUTING.md for install, typecheck, tests, and launching the TUI (bun dev) through Docker.

Benefits:

• Unblocks contributors on environments where bun is unavailable.
• Makes verification reproducible across machines with consistent Bun version.
• Reduces setup friction and helps contributors test fixes (including TUI behavior) before opening PRs.

Example commands:

• script/bun-docker.sh install
• script/bun-docker.sh run --cwd packages/tui typecheck
• script/bun-docker.sh run --cwd packages/tui test
• script/bun-docker.sh run dev .