Squadron creation dialogs render the folder picker at two sizes; form width is cramped #48

Problem

The same folder source picker (Local folder / Git URL / GitHub…) renders at two visibly different sizes depending on the path that opens it:

• First-run / setup form: mounts through the global command-palette popup (max-w-xl / max-h-105) — about 576×420.
• "Create Squadron…" from the scope dropdown: mounts inside the Squadron-create dialog (default popup max-w-lg, 512px) and picks up the nested-dialog 0.9 scale — about 518×378, visibly cramped for identical content.

Separately, the create-Squadron form itself is max-w-sm inside a max-w-lg dialog, so contents (notably the "Change folder" button row) don't span the dialog width.

Measured ownership

All the involved containers and popup classes are byte-identical to the merged creation surface (pre-picker-conversion); the picker-conversion PR changed only controlled props and copy in these files. This is a shared dialog-primitive / creation-surface layout issue, not part of any open PR.

Fix shape

Unify the picker's mounted size across both paths (same effective width/height regardless of entry door), and make the create-form contents span the dialog. Screenshots from Jackson's live session show both states.