Address review feedback: drop dead dragOrigin state, fix misplaced doc comment

Round-18 review flagged dragOrigin as write-only dead state left over from
a refactor, and a doc comment block describing stableDecimalPlaces sitting
above naturalDecimalPlaces instead.

Author: superhighfives

Pika/Views/EditableColorValue.swift

@@ -707,11 +707,6 @@ struct ColorComponentField: View {
         }
     }
 
-    /// Decimal places for a scrub session's live display: 2 by default — finer than that isn't a
-    /// meaningful step to scrub by (0.0001 of a 0...1 range is imperceptible per pixel) — unless
-    /// the value already displays with more precision than that, in which case keep it. Otherwise
-    /// starting a scrub would itself immediately truncate the value and reflow the row, before
-    /// any actual dragging has happened.
     /// Decimal places at which this component's per-pixel drag step is actually visible: the
     /// step is range-scaled (`dragUnitsPerPixel`), so a fixed 2 places leaves a fine-ranged
     /// component like OKLCH chroma advancing its last digit only every ~4px — which reads as the
@@ -723,6 +718,11 @@ struct ColorComponentField: View {
         return max(0, Int(ceil(-log10(step))))
     }
 
+    /// Decimal places for a scrub session's live display: 2 by default — finer than that isn't a
+    /// meaningful step to scrub by (0.0001 of a 0...1 range is imperceptible per pixel) — unless
+    /// the value already displays with more precision than that, in which case keep it. Otherwise
+    /// starting a scrub would itself immediately truncate the value and reflow the row, before
+    /// any actual dragging has happened.
     static func stableDecimalPlaces(for text: String) -> Int {
         guard let dotIndex = text.firstIndex(of: ".") else { return 2 }
         let decimals = text.distance(from: text.index(after: dotIndex), to: text.endIndex)

Pika/Views/ScrubTextField.swift

@@ -284,7 +284,6 @@ final class ScrubTextField: NSTextField {
     /// see the note at the `onFocusChange` assignment in `ScrubbableColorField.updateNSView`.
     var onFocusChange: ((Bool) -> Void)?
 
-    private var dragOrigin: Double?
     /// The most recent value `onDragChanged` reported — always set by the time `finishDrag` can
     /// run, since `updateDrag` fires at least once (immediately after `beginDrag`) before a
     /// `mouseUp` can be reached. Read once, then cleared, to hand `onDragEnd` its final value.
@@ -441,8 +440,7 @@ final class ScrubTextField: NSTextField {
     }
 
     private func beginDrag(at location: NSPoint) {
-        dragOrigin = Double(stringValue.trimmingCharacters(in: .whitespaces)) ?? 0
-        dragAnchorValue = dragOrigin
+        dragAnchorValue = Double(stringValue.trimmingCharacters(in: .whitespaces)) ?? 0
         dragAnchorX = location.x
         // Whichever is finer: the precision this component's drag step can actually resolve, or
         // the precision already on display (so starting a scrub never truncates what's shown).
@@ -508,7 +506,6 @@ final class ScrubTextField: NSTextField {
     }
 
     private func finishDrag() {
-        dragOrigin = nil
         dragAnchorValue = nil
         NSCursor.arrow.set()
         if let lastDragValue {