feat(cli): add shell completion (bash/zsh/fish) via @bomb.sh/tab #233

[MoMoUsama]

Closes #233

Summary

Adds shell auto-completion support to the Openship CLI using @bomb.sh/tab.

This introduces a new completion command that generates completion scripts for Bash, Zsh, and Fish from the live Commander command tree, ensuring commands, subcommands, and flags stay in sync automatically as the CLI evolves.

Scope

This PR implements static shell completion (commands, subcommands, and flags) only.

Dynamic value completion (e.g. project IDs, service names), as suggested in the issue, is intentionally left for a follow-up PR to keep this change focused and reviewable.

Changes

• Added openship completion <bash|zsh|fish>.
• Integrated @bomb.sh/tab with the CLI.
• Added end-to-end tests
• Documented shell completion setup in the README, including:
  • static completion scripts (recommended);
  • live-sourced completion.

Usage

openship completion bash
openship completion zsh
openship completion fish

Validation

• Completion scripts are generated successfully for Bash, Zsh, and Fish.
• Commands, subcommands, and flags complete as expected.
• Internal completion commands are not suggested.
• Existing CLI behavior remains unchanged.