Cloud project session can start without a repository checkout

Problem

A coordinated cloud project session can report successful creation even though it has no repository checkout, workspace path, or runnable terminal. The session then cannot perform the implementation or validation work it was created for, and the creator receives no provisioning error.

Reproduction

1. Create a coordinated cloud session for a configured repository project and an explicit base branch.
2. Allow the session to start automatically with a kickoff prompt that requires repository commands.
3. Inspect the session metadata and terminal.

Observed in session 8079b444-7187-470c-854f-ffa1f5ad74f2:

• Session type was cloud, but its path was empty.
• The process working directory was /.
• No Git checkout was available.
• The native terminal surface twice returned Terminal not found or not running.
• The session exhausted its attempt budget without reaching the requested work.

Expected behavior

• A cloud session created for a repository project starts with that repository and requested ref checked out in a runnable development environment.
• If repository/ref resolution or environment provisioning fails, session creation fails visibly with an actionable error.
• A repository-targeted cloud session never silently falls back to repository-less task state.

Acceptance criteria

• Cloud-task creation validates that a repository-targeted request has a complete owner and repository name before creating the task.
• A partial repository object, including branch without owner/name, is rejected rather than converted to the empty-repository sentinel.
• Provisioning failure is surfaced through project-session status and the kickoff turn.
• Tests cover repository-targeted cloud creation, explicit repository-less creation, partial repository metadata, and terminal/environment startup failure.
• Programmatic project-session creation receives the same Codespaces-scope and provisioning errors as interactive CLI flows.

Comienza en los puntos de entrada de la creación de tareas en la nube y del aprovisionamiento de sesiones de proyecto, y luego sigue el manejo de los metadatos del repositorio a través del inicio del entorno y del terminal. Ejecuta o añade cobertura para los casos dirigidos a un repositorio, explícitamente sin repositorio, con metadatos parciales y con fallos de aprovisionamiento, demostrando la finalización mediante errores de creación visibles o una sesión comprobada y ejecutable.