Switching the preview garment cleared the scene (print lost), and
re-loading a print used the canvas's hard-coded centred default instead
of the selected template.
- template_panel: add apply_current() to re-emit the selected template
for the current garment/print sizes and sync _current_state.
- main_window: remember the current print path, restore it after a
garment switch, and call apply_current() after garment/print changes
so the selected template stays sticky. Fine-tuned items are unaffected.
- Also feed template_applied into export_panel.set_transform to keep the
single-export transform in sync.
Docs: record the sticky-template rule (PRD 6.6).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>