fix: drop glare holes before the margin and never auto-pick specks

Filtering holes after the margin let -2 mm grow 1 mm specks past the
3 mm cutoff, and could drop real holes shrunk by a positive margin.

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

src/lib/app-state.svelte.ts

@@ -9,6 +9,7 @@ import type { Point, RasterImage, Shape } from './types';
 export type Tool = 'none' | 'scale' | 'seed' | 'draw';
 
 const DEFAULT_THRESHOLD = 128;
+const MIN_HOLE_MM = 3;
 
 export class AppState {
   // Raw: the cv module and pixel buffers must never be wrapped in reactive proxies.
@@ -43,7 +44,10 @@ export class AppState {
     if (this.mode === 'manual') {
       return shapeFromPolygons(cv, image.width, image.height, { outer: this.manualOuter, holes: this.manualHoles }, this.marginPx);
     }
-    return detect(cv, image, { threshold: this.threshold, invert: this.invert, seed: this.seed, marginPx: this.marginPx });
+    return detect(cv, image, {
+      threshold: this.threshold, invert: this.invert, seed: this.seed, marginPx: this.marginPx,
+      minHolePx: this.pxPerMm ? MIN_HOLE_MM * this.pxPerMm : 0,
+    });
   });
 
   exportShape = $derived(this.shapePx && this.pxPerMm ? prepareForExport(this.shapePx, this.pxPerMm) : null);