CAM routing refactor, area operation, and taper ball tool implementation

Major routing improvements:
- Refactor depth-first routing algorithm for better path optimization
- Reimplemented outline, roughing, pocket, and trace as area operation wrappers
- Add pocket shadow travel routing with optimized descent using travel bounds
- Improve contour routing with arc detection and polyEmit arc strategy
- Add area smoothing and ease-down options
- Fix outline handling with thru holes and surface reversal on tip2tip
- Move widget shadow methods into widget class for faster hole detection
- Better camInnerFirst support and proper feed/plunge defaults

Tool system improvements:
- Implement taper ball tool type with full support
- Add renderTool2() for profile-based visualization
- Convert tool menu to init code with bound vars
- Fix auto tool and auto spindle for prep operations
- Update tool profile generation for taperball geometry
- Add calcTaperBallExtent() for proper ball tangency calculations

Code cleanup:
- Remove duplicated slicer code from specialized slicers
- Asyncify shadowAt operations
- Deprecate pocket engrave operation
- Simplify upNover implementation
- Fix animation with new tool+settings requirements

src/kiri/mode/cam/op-drill.js

@@ -21,9 +21,11 @@ class OpDrill extends CamOp {
             drillToolDiam = drillTool.fluteDiameter(),
             sliceOut = this.sliceOut = [];
 
+        const allDrills = drills[widget.id] ?? []
+        if (allDrills.length === 0) return;
+
         updateToolDiams(drillToolDiam);
 
-        const allDrills = drills[widget.id] ?? []
         // drill points to use center (average of all points) of the polygon
         allDrills.forEach((drill) => {
             if (!drill.selected) {
@@ -61,9 +63,10 @@ class OpDrill extends CamOp {
         let { op, sliceOut } = this;
         let { setTool, setSpindle, setDrill, emitDrills } = ops;
 
+        if (sliceOut.length === 0) return;
+
         setTool(op.tool, undefined, op.rate);
         setDrill(op.down, op.lift, op.dwell);
-        setSpindle(op.spindle);
         emitDrills(sliceOut.map(slice => slice.camLines).flat());
     }
 }