mailu: full nox module — client, tools and events (ADR 0044/0046)

Email server. Users/aliases/domains over the admin REST API, mail read via
doveadm in the imap container; ten tools. Emits user/alias created/deleted by
polling and diffing the admin API, so a change in the web admin is announced
as readily as one via a tool. Consumes nothing — deliberately, since mutating
mail accounts off another module's event could silently lose mail. Typechecks
against the sdk; manifest parses.

Claude-Session: https://claude.ai/code/session_01LrgweAeERJYBg88c5cKDzF

modules/mailu/index.ts

@@ -0,0 +1,61 @@
+// mailu's events. The tool runtime imports this once the broker is bound. It watches the mail
+// server's accounts and announces what changed, so the rest of the mesh can react to a mailbox
+// appearing or an alias being pointed somewhere new.
+//
+// Emits (novox/hq ADR 0046/0047):
+//   module.mailu.user.created / .deleted     — a mailbox appeared or was removed
+//   module.mailu.alias.created / .deleted    — an alias was added or removed
+//
+// Consumes: nothing. Mail accounts are not something the mesh should mutate in the background off
+// another module's event — a wrong reaction here silently loses mail. mailu observes and announces;
+// it does not act on what others do. If a real consumer is ever wanted, it is a deliberate addition.
+//
+// Detection is by polling the admin API and diffing, exactly as plex diffs its sessions: the change
+// may have come from the web admin as easily as from a tool, and a diff catches both. The first
+// look primes silently, or a restart would re-announce every existing account as freshly created.
+
+import { emit } from "@novox/mesh-sdk/events";
+import { MailuClient } from "./client.js";
+
+const mailu = MailuClient.fromEnv();
+
+// A generic diff over a keyed set: emit `created` for keys that appeared, `deleted` for keys that
+// went away, and stay silent until primed. Users and aliases are the same shape of watch.
+function watcher(created: string, deleted: string): (keys: string[]) => Promise<void> {
+  const known = new Set<string>();
+  let primed = false;
+  return async (keys: string[]) => {
+    const now = new Set(keys);
+    if (primed) {
+      for (const key of now) if (!known.has(key)) await emit(created, { email: key });
+      for (const key of known) if (!now.has(key)) await emit(deleted, { email: key });
+    }
+    known.clear();
+    for (const key of now) known.add(key);
+    primed = true;
+  };
+}
+
+const watchUsers = watcher("module.mailu.user.created", "module.mailu.user.deleted");
+const watchAliases = watcher("module.mailu.alias.created", "module.mailu.alias.deleted");
+
+async function pollUsers(): Promise<void> {
+  await watchUsers((await mailu.listUsers()).map((u) => u.email));
+}
+
+async function pollAliases(): Promise<void> {
+  await watchAliases((await mailu.listAliases()).map((a) => a.email));
+}
+
+const tick = (fn: () => Promise<void>, everyMs: number): void => {
+  const runOnce = (): void => void fn().catch((err) => console.error(`[mailu] ${err}`));
+  setInterval(runOnce, everyMs);
+  runOnce();
+};
+
+// Accounts and aliases change on human time, not machine time — a minute's latency is fine, and
+// polling the admin API harder buys immediacy nobody asked for.
+tick(pollUsers, 60_000);
+tick(pollAliases, 60_000);
+
+console.log("[mailu] watching users and aliases");