feat: complete UI redesign — editorial-paper palette, Monaco theme, lucide icons, primitives

Palette overhaul:
- Warm cream canvas (#faf8f4) + near-white surfaces (#fdfdfb) + deep teal accent (#0f766e)
- Unified on stone-warm neutrals via @theme block in index.css

Typography:
- Inter Variable + JetBrains Mono Variable via fontsource (self-hosted)
- Monaco editor set to JetBrains Mono for consistency

Icons:
- lucide-react replaces all 8 hand-rolled SVGs
- Leaf brand mark beside wordmark

Shared primitives (src/components/ui/):
- Icon, Button (4 variants, 2 sizes), IconButton, TextInput, SectionHeader, StatusDot, Chip

Custom Monaco theme (src/theme/monaco-theme.ts):
- typst-leaf-light: warm near-white background, restrained rainbow-free syntax
- Keywords teal, strings warm green, comments stone italic, most tokens ink

Component reworks:
- TopBar: Leaf icon, h-12, chip-based status, Button/IconButton primitives
- Sidebar: w-72, icon+label tabs with teal bottom border
- StatusBar: lucide GitBranch/ArrowUp/ArrowDown, chip-based status
- FileTree: lucide Plus/FolderPlus/Pencil/Trash2, teal active state
- GitPanel: lucide status icons, restored staged/unstaged bg tint
- Preview: RotateCw reload icon, chip status
- EmptyState: muted Leaf icon
- ToastHost: StatusDot + lucide X

Fixes:
- GitPanel staged/unstaged/untracked rows now have distinct bg tints
- Button defaults to type="button" to prevent accidental form submission
- Editor error fallback from red-400 to rose-600
- DESIGN.md: removed emoji from layout skeleton, fixed Modals/Monaco typo

Build: pnpm -r typecheck + pnpm build pass.

pnpm-lock.yaml

@@ -48,6 +48,12 @@ importers:
 
   typst-leaf-frontend:
     dependencies:
+      '@fontsource-variable/inter':
+        specifier: ^5.2.8
+        version: 5.2.8
+      '@fontsource-variable/jetbrains-mono':
+        specifier: ^5.2.8
+        version: 5.2.8
       '@monaco-editor/react':
         specifier: ^4.7.0
         version: 4.7.0(monaco-editor@0.55.1)(react-dom@19.2.7(react@19.2.7))(react@19.2.7)
@@ -57,6 +63,9 @@ importers:
       '@tauri-apps/plugin-opener':
         specifier: ^2
         version: 2.5.4
+      lucide-react:
+        specifier: ^1.23.0
+        version: 1.23.0(react@19.2.7)
       monaco-editor:
         specifier: ^0.55.1
         version: 0.55.1
@@ -339,6 +348,12 @@ packages:
     cpu: [x64]
     os: [win32]
 
+  '@fontsource-variable/inter@5.2.8':
+    resolution: {integrity: sha512-kOfP2D+ykbcX/P3IFnokOhVRNoTozo5/JxhAIVYLpea/UBmCQ/YWPBfWIDuBImXX/15KH+eKh4xpEUyS2sQQGQ==}
+
+  '@fontsource-variable/jetbrains-mono@5.2.8':
+    resolution: {integrity: sha512-WBA9elru6Jdp5df2mES55wuOO0WIrn3kpXnI4+W2ek5u3ZgLS9XS4gmIlcQhiZOWEKl95meYdvK7xI+ETLCq/Q==}
+
   '@jridgewell/gen-mapping@0.3.13':
     resolution: {integrity: sha512-2kkt/7niJ6MgEPxF0bYdQ6etZaA+fQvDcLKckhy1yIQOzaoKjBBjSj63/aLVjYE3qhRt5dvM+uUyfCg6UKCBbA==}
 
@@ -1076,6 +1091,11 @@ packages:
   lru-cache@5.1.1:
     resolution: {integrity: sha512-KpNARQA3Iwv+jTA0utUVVbrh+Jlrr1Fv0e56GGzAFOXN7dk/FviaDW8LHmK52DlcH4WP2n6gI8vN1aesBFgo9w==}
 
+  lucide-react@1.23.0:
+    resolution: {integrity: sha512-38BpJcD0JhFosxHApP/BYsBetLpQFRoTRzEzstM/XCc3jsAG7wqaY1lgVwxiUe3xqYE+lNxo2PkCmYwXWrwwIw==}
+    peerDependencies:
+      react: ^16.5.1 || ^17.0.0 || ^18.0.0 || ^19.0.0
+
   magic-string@0.30.21:
     resolution: {integrity: sha512-vd2F4YUyEXKGcLHoq+TEyCjxueSeHnFxyyjNp80yg0XV4vUhnDer/lvvlqM/arB5bXQN5K2/3oinyCRyx8T2CQ==}
 
@@ -1565,6 +1585,10 @@ snapshots:
   '@esbuild/win32-x64@0.28.1':
     optional: true
 
+  '@fontsource-variable/inter@5.2.8': {}
+
+  '@fontsource-variable/jetbrains-mono@5.2.8': {}
+
   '@jridgewell/gen-mapping@0.3.13':
     dependencies:
       '@jridgewell/sourcemap-codec': 1.5.5
@@ -2224,6 +2248,10 @@ snapshots:
     dependencies:
       yallist: 3.1.1
 
+  lucide-react@1.23.0(react@19.2.7):
+    dependencies:
+      react: 19.2.7
+
   magic-string@0.30.21:
     dependencies:
       '@jridgewell/sourcemap-codec': 1.5.5