Make navigation dialogs compact and palette-style

Dialog titles drop to the base size at weight 600 with tighter spacing.
Search documents and Add project become command palettes: the search
field is the header, rows are single-line, arrow keys move between the
field and rows, and secondary details stay quiet. "Add Project" becomes
"Add project".

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>