Synth-mapping-helper

There is now a new button to create "lightnings" that zigzag between two rails (or staying on the "primary" rail if there is no other rail). The primary rail is the one that starts first or ends later.


Note this always creates a two-handed rail between left and right hand, but you can delete the "guides" and change the rail type afterwards (shift leftclick the rail in the editor to change type, or use the "change to X" buttons in SMH.

There now is a "short rails **to** length" button (the ruler-scissor, not scissor-ruler, that stays "shorten rails **by** amount").

I also reorganized the Wall-Art controls popup and made it more visible, so maybe more people read it.

But the main reason is updating dependencies and supporting python 3.13.

When uploading .synth files directly output by SMH, they would be refused with an internal server error.

Now they work, which required explicitly encoding one part in a very specific way (which is notably different from another part of the same type).

Fix typo preventing filters from working and an issue interpolating extremely short rails.

* Filter can now by quickly disabled completely, or disable type and rail filters separately.
* Single notes are no longer 0-length rails. but a separate filter option. This avoids the intuitive interaction with splitting rails (or smoothing) as mentioned in the last release.
* You can filter by node-count now too
Note that in this screenshot, the filter matches all rails that have at least 3 nodes (including rail head) **AND** node spacing between 1/16 and 1/4. Rails must match **ALL** configured filters (not just one).

Dashboard Filters
You can now filter by:
* Type. You can also quickly invert the type selection using the toggle above. I hope the icons are intuitive.
* Rail length. Note that **single notes count as 0-length rail**, so setting the "Min" to above 0 will also ignore all single notes, which makes some functionality not work, like splitting rails
* Rail spacing. This is fairly useful when you want to ignore buzzrails or long straight rails for smoothing.

Let me know if the filter doesn't work as expected for any operation (I tested many combinations, but obviously not everything).

I also updated the rest of the top bar to be more icons+tooltips and less visible text, and there is now a "pick pivot" button.

Snap-Smoothing
There are now three modes for smoothing:
* "Snap" (Arrow symbol) first smoothes the rail and then snaps single notes to the smoothed rail
* "Anchor" ensures the smoothed rail passes through all single notes
* "Tempoary Anchors" as above, but the single notes are auto-removed (this assumes you placed temporary anchor notes you want removed)