feat(skill): wire bd mail delegate via bb shim

skills/beadboard-driver/scripts/bb-mail-shim.mjs

@@ -0,0 +1,68 @@
+#!/usr/bin/env node
+import { spawnSync } from 'node:child_process';
+
+function getAgentName() {
+  const agent = (process.env.BB_AGENT || process.env.BD_ACTOR || '').trim();
+  if (!agent) {
+    console.error(
+      'bb-mail-shim: agent identity required.\n' +
+      'Set BB_AGENT before running bd mail, e.g. export BB_AGENT=silver-scribe',
+    );
+    process.exit(1);
+  }
+  return agent;
+}
+
+function runBbAgent(args) {
+  const result = spawnSync('bb', ['agent', ...args], { stdio: 'inherit', shell: false });
+  if (result.error) {
+    if (result.error.code === 'ENOENT') {
+      console.error('bb-mail-shim: bb command not found in PATH.');
+    } else {
+      console.error(`bb-mail-shim: failed to execute bb: ${result.error.message}`);
+    }
+    process.exit(1);
+  }
+  process.exit(result.status ?? 0);
+}
+
+const args = process.argv.slice(2);
+const subcommand = args[0];
+const agent = getAgentName();
+
+if (!subcommand || subcommand === '--help' || subcommand === '-h') {
+  console.log('Usage: bd mail inbox|send|read|ack ... (delegated via bb-mail-shim)');
+  process.exit(0);
+}
+
+switch (subcommand) {
+  case 'inbox':
+    runBbAgent(['inbox', '--agent', agent, ...args.slice(1)]);
+    break;
+  case 'send': {
+    const rest = args.slice(1);
+    const hasFrom = rest.includes('--from');
+    runBbAgent(['send', ...(hasFrom ? [] : ['--from', agent]), ...rest]);
+    break;
+  }
+  case 'read': {
+    const messageId = args[1];
+    if (!messageId) {
+      console.error('bb-mail-shim: read requires <message-id>');
+      process.exit(1);
+    }
+    runBbAgent(['read', '--agent', agent, '--message', messageId, ...args.slice(2)]);
+    break;
+  }
+  case 'ack': {
+    const messageId = args[1];
+    if (!messageId) {
+      console.error('bb-mail-shim: ack requires <message-id>');
+      process.exit(1);
+    }
+    runBbAgent(['ack', '--agent', agent, '--message', messageId, ...args.slice(2)]);
+    break;
+  }
+  default:
+    runBbAgent([subcommand, ...args.slice(1)]);
+}