feat(commandboard-api): expose AgentMail (agentbbs mailbox) routes (#86)

Mount @logicsrc/plugin-agentmail in the CommandBoard API so members can
list/read/search/send mail over the existing agentbbs Mailu server.

- src/agentmail.ts: inject imapflow + nodemailer + mailparser drivers into
  the plugin's Mailu transport (kept out of the plugin by design); env-driven
  builder (AGENTMAIL_BACKEND=mailu → bbs Mailu, else in-memory singleton for
  dev/test). Handles STARTTLS cert-vs-loopback via AGENTMAIL_SMTP_TLS_SERVERNAME.
- index.ts: register agentMailPlugin + 7 routes under /api/plugins/agentmail/*
  (mailboxes, list, read, search, send, PATCH flags, delete). Acting member
  from x-agentmail-member header (else AGENTMAIL_MEMBER), paid-gated;
  MailAccessError->402, DraftError->422.
- 6 route tests (in-memory backend) + contract test plugin-id list updated.
  commandboard-api 20/20, builds clean.

Note: run `npm install` to refresh the lockfile for the 3 new deps.

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

apps/commandboard-api/package.json

@@ -13,6 +13,7 @@
   },
   "dependencies": {
     "@logicsrc/plugin-core": "file:../../packages/plugin-core",
+    "@logicsrc/plugin-agentmail": "file:../../plugins/agentmail",
     "@logicsrc/plugin-c0mpute": "file:../../plugins/c0mpute",
     "@logicsrc/plugin-coinpay": "file:../../plugins/coinpay",
     "@logicsrc/plugin-email-accounts": "file:../../plugins/email-accounts",
@@ -20,9 +21,14 @@
     "@logicsrc/plugin-sh1pt": "file:../../plugins/sh1pt",
     "@logicsrc/plugin-social-accounts": "file:../../plugins/social-accounts",
     "@logicsrc/plugin-ugig": "file:../../plugins/ugig",
-    "@logicsrc/validators": "file:../../packages/validators"
+    "@logicsrc/validators": "file:../../packages/validators",
+    "imapflow": "^1.4.3",
+    "mailparser": "^3.9.12",
+    "nodemailer": "^9.0.1"
   },
   "devDependencies": {
+    "@types/mailparser": "^3.4.6",
+    "@types/nodemailer": "^8.0.1",
     "tsx": "^4.21.0",
     "vitest": "^4.0.8"
   }