feat(app): add open command for existing repo workspaces

[skulidropek]

Summary

• add docker-git open as an alias to open existing project workspaces by repo/issue URL (same project-dir resolution as attach)
• add top-level pnpm open <url> shortcut flow, mirroring existing pnpm clone behavior
• fix CI lint regression by splitting buildCreateCommand into a compose helper to satisfy max-lines-per-function

Verification

• pnpm -C packages/lib lint
• pnpm --filter ./packages/lib typecheck
• pnpm --filter ./packages/app test

Closes #75

Supersedes #81 (fork CI checks were not being triggered for latest commits).