fix: double editor column min-width from 400px to 800px

Rework: increase editor minimum width per feedback. Updates CSS,
layout constants, tests, and tauri.conf.json minWidth (800→1200).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src-tauri/tauri.conf.json

@@ -16,7 +16,7 @@
         "title": "Laputa",
         "width": 1400,
         "height": 900,
-        "minWidth": 800,
+        "minWidth": 1200,
         "minHeight": 400,
         "resizable": true,
         "fullscreen": false,

src/App.css

@@ -39,7 +39,7 @@
 
 .app__editor {
   flex: 1;
-  min-width: 400px;
+  min-width: 800px;
   min-height: 0;
   overflow: hidden;
   display: flex;

src/hooks/useLayoutPanels.test.ts

@@ -6,7 +6,7 @@ describe('useLayoutPanels', () => {
   it('exports column minimum widths', () => {
     expect(COLUMN_MIN_WIDTHS.sidebar).toBe(180)
     expect(COLUMN_MIN_WIDTHS.noteList).toBe(220)
-    expect(COLUMN_MIN_WIDTHS.editor).toBe(400)
+    expect(COLUMN_MIN_WIDTHS.editor).toBe(800)
     expect(COLUMN_MIN_WIDTHS.inspector).toBe(240)
   })
 

src/hooks/useLayoutPanels.ts

@@ -3,7 +3,7 @@ import { useCallback, useState } from 'react'
 export const COLUMN_MIN_WIDTHS = {
   sidebar: 180,
   noteList: 220,
-  editor: 400,
+  editor: 800,
   inspector: 240,
 } as const