fix(docker-git): prefer live runtime and block duplicate identities

[skulidropek]

Summary

• return Docker stderr in command failures instead of a bare DockerCommandError
• block duplicate docker-git container/service/volume identities unless --force replaces the existing project
• make open prefer the live runtime owner and attach to the running container before falling back to up

Verification

• pnpm -C packages/app exec vitest run tests/docker-git/create-project-identity-conflict.test.ts tests/docker-git/open-project.test.ts tests/docker-git/docker-runtime-info.test.ts
• pnpm -C packages/lib exec vitest run tests/usecases/create-project-docker-identities.test.ts tests/usecases/errors.test.ts
• pnpm -C packages/api exec vitest run tests/projects.test.ts
• pnpm -C packages/app typecheck
• pnpm -C packages/lib typecheck
• pnpm -C packages/api typecheck
• pnpm --filter ./packages/app build:docker-git