feat(iios): register EmailAdapter for EMAIL + email-shaped egress provider

AdapterRegistry now backs the EMAIL channel with the email-native EmailAdapter
(RFC threading) instead of the generic WebhookAdapter. Adds EmailProvider — an
email-envelope egress provider ({to,subject,text,html,inReplyTo}) registered for
EMAIL when IIOS_PROVIDER_URL_EMAIL is set (sandbox stays the default). Spec:
signed email → normalized interaction on the email thread; a reply joins the
same thread (one conversation); bad signature → rejected (fail-closed).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/iios-service/src/capability/capability.registry.ts

@@ -2,6 +2,7 @@ import { Injectable, NotFoundException } from '@nestjs/common';
 import type { CapabilityProvider } from '@insignia/iios-contracts';
 import { SandboxProvider } from './sandbox.provider';
 import { HttpProvider } from './http.provider';
+import { EmailProvider } from './email.provider';
 
 const DEFAULT_CHANNELS = ['WEBHOOK', 'EMAIL', 'WHATSAPP', 'PORTAL'];
 
@@ -19,7 +20,9 @@ export class CapabilityProviderRegistry {
     for (const ch of DEFAULT_CHANNELS) this.register(new SandboxProvider([ch]));
     for (const ch of DEFAULT_CHANNELS) {
       const url = process.env[`IIOS_PROVIDER_URL_${ch}`];
-      if (url) this.register(new HttpProvider(ch, url));
+      if (!url) continue;
+      // EMAIL gets an email-shaped envelope provider; other channels use the generic HTTP one.
+      this.register(ch === 'EMAIL' ? new EmailProvider(url) : new HttpProvider(ch, url));
     }
   }
 

packages/iios-service/src/capability/email.provider.ts

@@ -0,0 +1,40 @@
+import type { CapabilityProvider, CapabilityRequest, ProviderResult } from '@insignia/iios-contracts';
+
+interface EmailPayload {
+  subject?: string;
+  text?: string;
+  html?: string;
+  inReplyTo?: string;
+}
+
+/**
+ * Email egress provider: shapes the outbound command into an email envelope
+ * ({to, subject, text, html, inReplyTo}) and POSTs it to a configured send endpoint
+ * (a vendor mail API / SMTP relay behind a URL). Activated only when
+ * IIOS_PROVIDER_URL_EMAIL is set; a transport failure is surfaced as FAILED, never thrown.
+ */
+export class EmailProvider implements CapabilityProvider {
+  readonly name = 'email-http';
+  readonly channelTypes = ['EMAIL'];
+  readonly capabilities = { canSend: true };
+
+  constructor(private readonly url: string) {}
+
+  async send(req: CapabilityRequest): Promise<ProviderResult> {
+    const started = Date.now();
+    const p = (req.payload ?? {}) as EmailPayload;
+    const email = { to: req.target, subject: p.subject ?? '(no subject)', text: p.text, html: p.html, inReplyTo: p.inReplyTo };
+    try {
+      const res = await fetch(this.url, {
+        method: 'POST',
+        headers: { 'content-type': 'application/json', 'idempotency-key': req.idempotencyKey },
+        body: JSON.stringify(email),
+      });
+      const latencyMs = Date.now() - started;
+      if (!res.ok) return { providerRef: `email-${res.status}`, outcome: 'FAILED', errorCode: `HTTP_${res.status}`, latencyMs };
+      return { providerRef: `email-${req.idempotencyKey}`, outcome: 'SENT', latencyMs };
+    } catch (err) {
+      return { providerRef: 'email-error', outcome: 'FAILED', errorCode: (err as Error).message.slice(0, 60), latencyMs: Date.now() - started };
+    }
+  }
+}