feat(v2): add permission mode passthrough and fix agent stop-on-close

- Add permission_mode field to AgentQueryOptions (Rust, sidecar, bridge)
  flowing from controller through sidecar to SDK; defaults to
  bypassPermissions, supports default mode
- Fix AgentPane onDestroy bug: remove stopAgent() from onDestroy (fires
  on layout remounts), move stop-on-close to TilingGrid onClose handler
- Bundle SDK into sidecar via esbuild (remove --external flag)

v2/src/lib/components/Agent/AgentPane.svelte

@@ -1,5 +1,5 @@
 <script lang="ts">
-  import { onMount, onDestroy } from 'svelte';
+  import { onMount } from 'svelte';
   import { marked, Renderer } from 'marked';
   import { queryAgent, stopAgent, isAgentReady, restartAgent } from '../../adapters/agent-bridge';
   import {
@@ -68,11 +68,8 @@
     }
   });
 
-  onDestroy(() => {
-    if (session?.status === 'running' || session?.status === 'starting') {
-      stopAgent(sessionId).catch(() => {});
-    }
-  });
+  // NOTE: Do NOT stop agents in onDestroy — it fires on layout changes/remounts,
+  // not just explicit close. Stop-on-close is handled by TilingGrid.
 
   let followUpPrompt = $state('');