doctor: probe canonical editable-install module
sol_importable_check was probing import sol, but there is no top-level
sol package. The editable install registers think as the top-level module,
so the probe either skipped with no .venv or failed on every install.
The Makefile already uses the canonical form
from think.sol_cli import main at lines 69 and 72.
Update the probe to match that import and update the match string and
detail strings to reference think instead of sol.
Keep the check name sol_importable to avoid rename churn.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>