Bug fixed: Manual mode still auto-solved while adjusting sliders (#41)

[everyday3d]

Bug: Manual mode still auto-solved while adjusting sliders (#41)

Symptom: after switching to Manual mode, dragging layer sliders felt like the auto-solver was still running.

Root cause: two things. In Faithful mode every slider step rebuilt the whole relief with the colour-match solver (about 157 ms per step, and a 3-layer move changed the height of about 19% of the picture). Separately, changing a spool, reordering, adding or removing a slot, or moving the Base Layer Thickness slider re-solved or reset the swap layers the user had set by hand.

Reproduction: Manual Mode, drag a layer slider or swap a spool on the sample portrait.

Resolution: the relief holds still during a drag and updates once on release, hand-set swap layers are kept, and a new Relief in Manual mode switch lets you choose Match photo or Fixed relief. Commit 39d7748