feat: make color manipulation sliders reactive with auto-apply

Remove redundant "Apply" buttons and make all manipulation sliders (lighten, darken, saturate, desaturate, rotate) update the color in real-time with 300ms debouncing. This provides a smoother, more intuitive user experience.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

components/tools/ManipulationPanel.tsx

@@ -1,6 +1,6 @@
 'use client';
 
-import { useState } from 'react';
+import { useState, useEffect, useRef } from 'react';
 import { Slider } from '@/components/ui/slider';
 import { Button } from '@/components/ui/button';
 import {
@@ -32,80 +32,112 @@ export function ManipulationPanel({ color, onColorChange }: ManipulationPanelPro
   const rotateMutation = useRotate();
   const complementMutation = useComplement();
 
-  const handleLighten = async () => {
-    try {
-      const result = await lightenMutation.mutateAsync({
-        colors: [color],
-        amount: lightenAmount,
-      });
-      if (result.colors[0]) {
-        onColorChange(result.colors[0].output);
-        toast.success(`Lightened by ${(lightenAmount * 100).toFixed(0)}%`);
-      }
-    } catch (error) {
-      toast.error('Failed to lighten color');
-    }
-  };
+  // Debounce timers
+  const lightenTimer = useRef<NodeJS.Timeout>();
+  const darkenTimer = useRef<NodeJS.Timeout>();
+  const saturateTimer = useRef<NodeJS.Timeout>();
+  const desaturateTimer = useRef<NodeJS.Timeout>();
+  const rotateTimer = useRef<NodeJS.Timeout>();
 
-  const handleDarken = async () => {
-    try {
-      const result = await darkenMutation.mutateAsync({
-        colors: [color],
-        amount: darkenAmount,
-      });
-      if (result.colors[0]) {
-        onColorChange(result.colors[0].output);
-        toast.success(`Darkened by ${(darkenAmount * 100).toFixed(0)}%`);
+  // Reactive lighten
+  useEffect(() => {
+    if (lightenTimer.current) clearTimeout(lightenTimer.current);
+    lightenTimer.current = setTimeout(async () => {
+      if (lightenAmount > 0) {
+        try {
+          const result = await lightenMutation.mutateAsync({
+            colors: [color],
+            amount: lightenAmount,
+          });
+          if (result.colors[0]) {
+            onColorChange(result.colors[0].output);
+          }
+        } catch (error) {
+          // Silent error - user is still adjusting
+        }
       }
-    } catch (error) {
-      toast.error('Failed to darken color');
-    }
-  };
+    }, 300);
+  }, [lightenAmount]);
 
-  const handleSaturate = async () => {
-    try {
-      const result = await saturateMutation.mutateAsync({
-        colors: [color],
-        amount: saturateAmount,
-      });
-      if (result.colors[0]) {
-        onColorChange(result.colors[0].output);
-        toast.success(`Saturated by ${(saturateAmount * 100).toFixed(0)}%`);
+  // Reactive darken
+  useEffect(() => {
+    if (darkenTimer.current) clearTimeout(darkenTimer.current);
+    darkenTimer.current = setTimeout(async () => {
+      if (darkenAmount > 0) {
+        try {
+          const result = await darkenMutation.mutateAsync({
+            colors: [color],
+            amount: darkenAmount,
+          });
+          if (result.colors[0]) {
+            onColorChange(result.colors[0].output);
+          }
+        } catch (error) {
+          // Silent error - user is still adjusting
+        }
       }
-    } catch (error) {
-      toast.error('Failed to saturate color');
-    }
-  };
+    }, 300);
+  }, [darkenAmount]);
 
-  const handleDesaturate = async () => {
-    try {
-      const result = await desaturateMutation.mutateAsync({
-        colors: [color],
-        amount: desaturateAmount,
-      });
-      if (result.colors[0]) {
-        onColorChange(result.colors[0].output);
-        toast.success(`Desaturated by ${(desaturateAmount * 100).toFixed(0)}%`);
+  // Reactive saturate
+  useEffect(() => {
+    if (saturateTimer.current) clearTimeout(saturateTimer.current);
+    saturateTimer.current = setTimeout(async () => {
+      if (saturateAmount > 0) {
+        try {
+          const result = await saturateMutation.mutateAsync({
+            colors: [color],
+            amount: saturateAmount,
+          });
+          if (result.colors[0]) {
+            onColorChange(result.colors[0].output);
+          }
+        } catch (error) {
+          // Silent error - user is still adjusting
+        }
       }
-    } catch (error) {
-      toast.error('Failed to desaturate color');
-    }
-  };
+    }, 300);
+  }, [saturateAmount]);
 
-  const handleRotate = async () => {
-    try {
-      const result = await rotateMutation.mutateAsync({
-        colors: [color],
-        amount: rotateAmount,
-      });
-      if (result.colors[0]) {
-        onColorChange(result.colors[0].output);
-        toast.success(`Rotated hue by ${rotateAmount}°`);
+  // Reactive desaturate
+  useEffect(() => {
+    if (desaturateTimer.current) clearTimeout(desaturateTimer.current);
+    desaturateTimer.current = setTimeout(async () => {
+      if (desaturateAmount > 0) {
+        try {
+          const result = await desaturateMutation.mutateAsync({
+            colors: [color],
+            amount: desaturateAmount,
+          });
+          if (result.colors[0]) {
+            onColorChange(result.colors[0].output);
+          }
+        } catch (error) {
+          // Silent error - user is still adjusting
+        }
       }
-    } catch (error) {
-      toast.error('Failed to rotate hue');
-    }
-  };
+    }, 300);
+  }, [desaturateAmount]);
+
+  // Reactive rotate
+  useEffect(() => {
+    if (rotateTimer.current) clearTimeout(rotateTimer.current);
+    rotateTimer.current = setTimeout(async () => {
+      if (rotateAmount !== 0) {
+        try {
+          const result = await rotateMutation.mutateAsync({
+            colors: [color],
+            amount: rotateAmount,
+          });
+          if (result.colors[0]) {
+            onColorChange(result.colors[0].output);
+          }
+        } catch (error) {
+          // Silent error - user is still adjusting
+        }
+      }
+    }, 300);
+  }, [rotateAmount]);
 
   const handleComplement = async () => {
     try {
@@ -130,7 +162,7 @@ export function ManipulationPanel({ color, onColorChange }: ManipulationPanelPro
   return (
     <div className="space-y-6">
       {/* Lighten */}
-      <div className="space-y-3">
+      <div>
         <Slider
           label="Lighten"
           min={0}
@@ -141,13 +173,10 @@ export function ManipulationPanel({ color, onColorChange }: ManipulationPanelPro
           suffix="%"
           showValue
         />
-        <Button onClick={handleLighten} disabled={isLoading} className="w-full">
-          Apply Lighten
-        </Button>
       </div>
 
       {/* Darken */}
-      <div className="space-y-3">
+      <div>
         <Slider
           label="Darken"
           min={0}
@@ -158,13 +187,10 @@ export function ManipulationPanel({ color, onColorChange }: ManipulationPanelPro
           suffix="%"
           showValue
         />
-        <Button onClick={handleDarken} disabled={isLoading} className="w-full">
-          Apply Darken
-        </Button>
       </div>
 
       {/* Saturate */}
-      <div className="space-y-3">
+      <div>
         <Slider
           label="Saturate"
           min={0}
@@ -175,13 +201,10 @@ export function ManipulationPanel({ color, onColorChange }: ManipulationPanelPro
           suffix="%"
           showValue
         />
-        <Button onClick={handleSaturate} disabled={isLoading} className="w-full">
-          Apply Saturate
-        </Button>
       </div>
 
       {/* Desaturate */}
-      <div className="space-y-3">
+      <div>
         <Slider
           label="Desaturate"
           min={0}
@@ -192,13 +215,10 @@ export function ManipulationPanel({ color, onColorChange }: ManipulationPanelPro
           suffix="%"
           showValue
         />
-        <Button onClick={handleDesaturate} disabled={isLoading} className="w-full">
-          Apply Desaturate
-        </Button>
       </div>
 
       {/* Rotate Hue */}
-      <div className="space-y-3">
+      <div>
         <Slider
           label="Rotate Hue"
           min={-180}
@@ -209,9 +229,6 @@ export function ManipulationPanel({ color, onColorChange }: ManipulationPanelPro
           suffix="°"
           showValue
         />
-        <Button onClick={handleRotate} disabled={isLoading} className="w-full">
-          Apply Rotation
-        </Button>
       </div>
 
       {/* Quick Actions */}