feat(v2): scaffold Tauri 2.x + Svelte 5 project (Phase 1)

- Tauri 2.10 + Svelte 5.45 + TypeScript + Vite 7
- Catppuccin Mocha theme with CSS variables and semantic aliases
- CSS Grid layout: sidebar (260px) + workspace, responsive breakpoints
  for ultrawide (3440px+) and narrow (<1200px)
- Component structure: Layout/, Terminal/, Agent/, Markdown/, Sidebar/
- Svelte 5 stores with $state runes: sessions, agents, layout
- SDK message adapter (abstracts Agent SDK wire format)
- PTY bridge (Tauri IPC wrapper, stubbed for Phase 2)
- Node.js sidecar entry point (stdio NDJSON, stubbed for Phase 3)
- Rust modules: pty, sidecar, watcher, session (stubbed)
- Vite dev server on port 9700
- Build verified: binary + .deb + .rpm + AppImage all produced

v2/src/lib/components/Layout/PaneContainer.svelte

@@ -0,0 +1,54 @@
+<script lang="ts">
+  import type { Snippet } from 'svelte';
+
+  interface Props {
+    title: string;
+    children: Snippet;
+  }
+
+  let { title, children }: Props = $props();
+</script>
+
+<div class="pane-container">
+  <div class="pane-header">
+    <span class="pane-title">{title}</span>
+  </div>
+  <div class="pane-content">
+    {@render children()}
+  </div>
+</div>
+
+<style>
+  .pane-container {
+    display: flex;
+    flex-direction: column;
+    background: var(--bg-secondary);
+    border-radius: var(--border-radius);
+    overflow: hidden;
+    border: 1px solid var(--border);
+  }
+
+  .pane-header {
+    height: var(--pane-header-height);
+    display: flex;
+    align-items: center;
+    padding: 0 10px;
+    background: var(--bg-tertiary);
+    border-bottom: 1px solid var(--border);
+    flex-shrink: 0;
+  }
+
+  .pane-title {
+    font-size: 12px;
+    font-weight: 500;
+    color: var(--text-secondary);
+    white-space: nowrap;
+    overflow: hidden;
+    text-overflow: ellipsis;
+  }
+
+  .pane-content {
+    flex: 1;
+    overflow: auto;
+  }
+</style>