fix: pass claude binary path to Agent SDK for packaged app

The SDK's query() function also needs to find the claude binary.
Added findClaudePath() in claude-client.ts and pass it via
pathToClaudeCodeExecutable option, fixing "Failed to create session"
in packaged builds where PATH is limited.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/lib/claude-client.ts

@@ -14,6 +14,53 @@ import type {
 } from '@anthropic-ai/claude-agent-sdk';
 import type { ClaudeStreamOptions, SSEEvent, TokenUsage, MCPServerConfig, PermissionRequestEvent } from '@/types';
 import { registerPendingPermission } from './permission-registry';
+import { execFileSync } from 'child_process';
+import os from 'os';
+import path from 'path';
+
+let cachedClaudePath: string | null | undefined;
+
+function findClaudePath(): string | undefined {
+  if (cachedClaudePath !== undefined) return cachedClaudePath || undefined;
+
+  const home = os.homedir();
+  const candidates = [
+    '/usr/local/bin/claude',
+    '/opt/homebrew/bin/claude',
+    path.join(home, '.npm-global', 'bin', 'claude'),
+    path.join(home, '.local', 'bin', 'claude'),
+    path.join(home, '.claude', 'bin', 'claude'),
+  ];
+
+  for (const p of candidates) {
+    try {
+      execFileSync(p, ['--version'], { timeout: 3000, stdio: 'pipe' });
+      cachedClaudePath = p;
+      return p;
+    } catch {
+      // not found
+    }
+  }
+
+  // Fallback: which claude
+  const extra = ['/usr/local/bin', '/opt/homebrew/bin', '/usr/bin', '/bin',
+    path.join(home, '.npm-global', 'bin'), path.join(home, '.nvm', 'current', 'bin'),
+    path.join(home, '.local', 'bin'), path.join(home, '.claude', 'bin')];
+  const current = (process.env.PATH || '').split(':');
+  for (const p of extra) { if (!current.includes(p)) current.push(p); }
+
+  try {
+    const result = execFileSync('/usr/bin/which', ['claude'], {
+      timeout: 3000, stdio: 'pipe',
+      env: { ...process.env, PATH: current.join(':') },
+    });
+    const found = result.toString().trim();
+    if (found) { cachedClaudePath = found; return found; }
+  } catch { /* not found */ }
+
+  cachedClaudePath = null;
+  return undefined;
+}
 
 /**
  * Convert our MCPServerConfig to the SDK's McpStdioServerConfig format
@@ -92,6 +139,12 @@ export function streamClaude(options: ClaudeStreamOptions): ReadableStream<strin
           permissionMode: (permissionMode as Options['permissionMode']) || 'acceptEdits',
         };
 
+        // Find claude binary for packaged app where PATH is limited
+        const claudePath = findClaudePath();
+        if (claudePath) {
+          queryOptions.pathToClaudeCodeExecutable = claudePath;
+        }
+
         if (model) {
           queryOptions.model = model;
         }