Problem: dropping a PSD/PSB file on the window imported it straight away.
The drop handler always passed `importAs` (Settings > Import > Default Drag
Import As) to `file.import`, and the Import Photoshop File form only opens
when `importAs` is missing, so the dialog that File > Import > File...
shows never appeared for drops.
Fix: a drop that includes a Photoshop file leaves `importAs` out, so the
form asks (other drops keep passing the preference). For dropped files the
form's Import Kind starts at Default Drag Import As; File > Import keeps
starting at Composition. The engine already falls back to the preference
for `drag` imports without `importAs`.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>