fix: inject Node.js bin dir into ACP child process PATH on Windows

ACP child processes spawn .cmd batch scripts (e.g. claude-agent-acp.cmd)
that internally invoke node.exe. When the host process PATH does not
include the Node.js installation directory, the child fails with
'node is not recognized as an internal or external command'.

Fix: prepend process.execPath's directory to the spawned env PATH,
with Windows-safe case-insensitive key lookup (Path vs PATH).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Long Chen (from Dev Box)

src/adapters/AcpAdapter.ts

@@ -308,6 +308,18 @@ export class AcpAdapter implements AgentAdapter {
         this.validateExecutable();
         const env = { ...process.env, ...extraEnv };
         this.sanitizeSpawnEnv(env);
+
+        // Ensure Node.js bin directory is in PATH so child .cmd scripts can find `node`
+        const nodeBinDir = path.dirname(process.execPath);
+        const pathKey = process.platform === 'win32'
+            ? Object.keys(env).find(k => k.toUpperCase() === 'PATH') || 'Path'
+            : 'PATH';
+        const currentPath = env[pathKey] || '';
+        if (!currentPath.split(path.delimiter).some(p => p.toLowerCase() === nodeBinDir.toLowerCase())) {
+            env[pathKey] = `${nodeBinDir}${path.delimiter}${currentPath}`;
+            debugLog('[AcpAdapter]', `Injected Node.js bin dir into PATH: ${nodeBinDir}`);
+        }
+
         const args = [...this.defaultArgs];
 
         debugLog('[AcpAdapter]', `Spawning: ${this.executable} ${args.join(' ')}`);