FIX bumpy flatmap smoothing skipped on the left hemisphere

[mvdoc]

Splits the bug fix out of #310 (which has been sitting since 2019 and no longer merges cleanly).

The bug

In mriview_surface.js, smoothfactor and smoothiter are declared with var inside the if (this.flatlims !== undefined) block, but used ~25 lines earlier in the same per-hemisphere loop to smooth wmareas and pialareas.

var hoists the declaration to function scope but not the assignment, so on the first iteration of the loop they are still undefined. iterativelySmoothVertexData then runs:

for ( var i = 0; i < undefined; i ++ ) { ... }

0 < undefined is false, so the loop body never executes and the areas come back completely unsmoothed. By the second iteration the values assigned during the first pass are visible, so:

• left hemisphere — areas unsmoothed
• right hemisphere — areas smoothed with factor 0.1, 50 iterations

which is why the two hemispheres have visibly different bump relief. I confirmed the bug is still present on current main.

The fix

Declare the parameters above the loop, split them into separate constants for the area and distance passes, and reduce the iteration counts (areas 50 → 5, dists 50 → 20) for a somewhat less smoothed result.

The commit adds a comment explaining why the declarations have to live outside the loop, so the bug does not get quietly reintroduced by re-nesting them.

Note for reviewers

The iteration-count reduction is a deliberate appearance change riding along with the correctness fix — it is part of what @alexhuth was going for in #310 ("I also reduced the amount of smoothing somewhat"), but it is separable if you would rather land the hoist alone first. These are also hardcoded constants; they could reasonably be exposed in [webgl_viewopts] next to bumpy_flatmap.

Testing

node --check passes. Not verified visually — no render was produced.

The lighting half of #310 is split into a separate PR.

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