Build fails after SDK upgrade because pinned sdk-version missing

The goal is to determine the correct CLI response when a project’s tiapp.xml pins an SDK version that is not present after an upgrade.

Constraints include the side‑by‑side installation model, the distinction between the global default SDK and the per‑project pin, the possibility of a partially extracted SDK that appears in the list but is unusable, and the variation in behavior across CLI and SDK major releases.

Uncertainty remains about whether the tool should halt with an explicit error, automatically fall back to the global default, or prompt the user to select an installed version.

Should the CLI emit a hard error and suggest installing the pinned version?

Should it silently fall back to the global default SDK?

Should it present an interactive choice of available SDKs?