docs: services.sms reference + phone-number OTP authentication guide (#2780)

The #2780 line shipped code without hand-written docs:

- new kernel/runtime-services/sms-service.mdx (mirrors email-service.mdx):
  send/isConfigured surface, no-persistence/no-body-logging red line,
  provider configuration via the `sms` settings namespace, consumers
  (auth OTP, messaging sms channel, import SMS invitations)
- permissions/authentication.mdx: Phone-Number Authentication section -
  OS_AUTH_PHONE_NUMBER_ENABLED, phone+password sign-in, the four OTP
  endpoints gated on a deliverable SMS service (features.phoneNumberOtp),
  abuse hardening (admission cooldown/cap, allowedAttempts, per-IP rules,
  no-oracle reset), import SMS invitations
- runtime-services index + meta: register the new page

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013LXUXU66dBaP3SSG4ZVtuH

Author: claude

.changeset/docs-sms-phone-otp.md

@@ -0,0 +1,6 @@
+---
+---
+
+Docs-only: `services.sms` runtime-service reference + phone-number
+authentication (SMS OTP) section in the authentication guide. No package
+changes.

content/docs/kernel/runtime-services/index.mdx

@@ -39,6 +39,7 @@ Each page links the canonical TypeScript source used to derive signatures.
 - Sharing: `packages/spec/src/contracts/sharing-service.ts`
 - Queue: `packages/spec/src/contracts/queue-service.ts`
 - Email: `packages/spec/src/contracts/email-service.ts`
+- SMS: `packages/spec/src/contracts/sms-service.ts`
 - Storage: `packages/spec/src/contracts/storage-service.ts`
 - Settings: `packages/services/service-settings/src/settings-service.ts`
 - Audit bridge: `packages/services/service-settings/src/settings-service.types.ts`

content/docs/kernel/runtime-services/meta.json

@@ -7,6 +7,7 @@
     "audit-service",
     "queue-service",
     "email-service",
+    "sms-service",
     "settings-service",
     "storage-service",
     "examples",

content/docs/kernel/runtime-services/sms-service.mdx

@@ -0,0 +1,70 @@
+---
+title: services.sms
+description: Outbound SMS delivery through pluggable providers (Aliyun SMS, Twilio).
+---
+
+# `services.sms`
+
+- **Stability:** `stable`
+- **Canonical source:** `packages/spec/src/contracts/sms-service.ts`
+
+## Methods
+
+```ts
+services.sms.send(input: SendSmsInput): Promise<SendSmsResult>
+services.sms.isConfigured(): boolean
+```
+
+`SendSmsInput` carries the recipient (`to`, E.164 recommended), the rendered
+`body`, and optional provider-template fields (`templateId`,
+`templateParams`) for template-only providers such as Aliyun SMS — which
+refuse free-form bodies and only deliver pre-registered templates.
+
+`isConfigured()` is `false` while the service runs on the development
+`LogSmsTransport` fallback (messages are logged, never delivered). Consumers
+that advertise SMS-dependent features — phone OTP sign-in, SMS invitations —
+gate on it in production (`features.phoneNumberOtp`).
+
+## Returns
+
+`SendSmsResult`:
+
+- `id: string` — correlation id for the attempt
+- `status: 'sent' | 'failed'`
+- `messageId?: string` — provider message id (Aliyun BizId, Twilio SID)
+- `error?: string` — transport detail when `status='failed'`
+
+## No persistence, no body logging
+
+Unlike `services.email` (which persists to `sys_email`), the SMS service
+deliberately has **no persistence surface and never logs message bodies**:
+SMS bodies routinely carry one-time passwords, so a message log would be a
+credential store. Diagnostics log masked recipients and statuses only.
+
+## Configuration
+
+Providers are configured through the `sms` settings namespace
+(Setup → Settings → SMS Delivery), with live rebinding — no restart needed:
+
+- `provider` — `log` (default, no real delivery) / `aliyun` / `twilio`
+- Aliyun: `aliyun_access_key_id`, `aliyun_access_key_secret` (encrypted),
+  `aliyun_sign_name`, `aliyun_template_code` (default catch-all template with
+  a single `${content}` variable for generic notification SMS)
+- Twilio: `twilio_account_sid`, `twilio_auth_token` (encrypted), and
+  `twilio_from_number` or `twilio_messaging_service_sid`
+
+Every key accepts the standard settings env override (`OS_SMS_PROVIDER`,
+`OS_SMS_ALIYUN_ACCESS_KEY_ID`, …). The **Send test SMS** action exercises the
+live (or unsaved) provider configuration.
+
+## Consumers
+
+- **Phone-number OTP auth** — sign-in verification codes and self-service
+  password-reset codes (`/phone-number/*`, see
+  [Authentication](/docs/permissions/authentication)).
+- **Messaging `sms` channel** — `notify(channels:['sms'])` resolves the
+  recipient's `sys_user.phone_number`, renders the `(topic, 'sms', locale)`
+  row from `sys_notification_template`, and delivers through this service
+  with outbox retry/dead-letter.
+- **Identity import SMS invitations** — the `invite` password policy sends a
+  credential-free invitation SMS to phone-only rows.

content/docs/permissions/authentication.mdx

@@ -270,6 +270,89 @@ const response = await fetch('http://localhost:3000/api/v1/auth/send-verificatio
 const response = await fetch(`http://localhost:3000/api/v1/auth/verify-email?token=${token}`);
 ```
 
+### Phone-Number Authentication (SMS OTP)
+
+Phone numbers are a first-class sign-in identifier (better-auth `phoneNumber`
+plugin). Opt in per deployment:
+
+```bash
+OS_AUTH_PHONE_NUMBER_ENABLED=true   # or auth.plugins.phoneNumber in config
+```
+
+The plugin adds `sys_user.phone_number` (unique) and `phone_number_verified`.
+Phone-only employees are created by the admin create-user / import routes with
+an undeliverable placeholder email (`u-<random>@placeholder.invalid`) — never
+by OTP self-signup.
+
+#### Phone + password sign-in
+
+Always available once the plugin is on:
+
+```typescript
+const response = await fetch('http://localhost:3000/api/v1/auth/sign-in/phone-number', {
+  method: 'POST',
+  headers: { 'Content-Type': 'application/json' },
+  body: JSON.stringify({ phoneNumber: '+8613800000000', password: 'password123' })
+});
+```
+
+#### OTP sign-in and self-service reset (requires SMS delivery)
+
+The OTP surface opens only when a **deliverable SMS service** is configured
+(`services.sms`, Setup → Settings → SMS Delivery); without one these endpoints
+fail loudly with `NOT_SUPPORTED`. The public config advertises real
+availability as `features.phoneNumberOtp`, which is what the Console login UI
+gates its "Sign in with verification code" mode and the SMS reset branch on.
+
+```typescript
+// Sign-in / verification: request a code, then verify (creates a session)
+await fetch('/api/v1/auth/phone-number/send-otp', {
+  method: 'POST',
+  headers: { 'Content-Type': 'application/json' },
+  body: JSON.stringify({ phoneNumber: '+8613800000000' })
+});
+await fetch('/api/v1/auth/phone-number/verify', {
+  method: 'POST',
+  headers: { 'Content-Type': 'application/json' },
+  body: JSON.stringify({ phoneNumber: '+8613800000000', code: '123456' })
+});
+
+// Self-service password reset over SMS
+await fetch('/api/v1/auth/phone-number/request-password-reset', {
+  method: 'POST',
+  headers: { 'Content-Type': 'application/json' },
+  body: JSON.stringify({ phoneNumber: '+8613800000000' })
+});
+await fetch('/api/v1/auth/phone-number/reset-password', {
+  method: 'POST',
+  headers: { 'Content-Type': 'application/json' },
+  body: JSON.stringify({ phoneNumber: '+8613800000000', otp: '123456', newPassword: 'NewPass123!' })
+});
+```
+
+Abuse hardening ships with the feature (SMS is a paid channel):
+
+- **Per-number admission guard** (always on): 60s cooldown + 5 sends per
+  rolling hour per number, shared across the sign-in and reset flows and —
+  in a cluster — across nodes via the shared KV. Rejected requests get an
+  honest `429` with the retry window and never invalidate an already
+  delivered code. Tune via `AuthManager` `phoneOtp`
+  (`cooldownSeconds` / `maxPerHour` / `allowedAttempts` / `expiresIn` /
+  `otpLength`).
+- **Wrong-code attempts** are capped at 3 (`allowedAttempts`), then the code
+  is invalidated.
+- **Per-IP rate limiting**: the plugin ships a `/phone-number/*` default
+  (10/min), and the `auth` settings `rate_limit_max` /
+  `rate_limit_window_seconds` tighten all four OTP endpoints.
+- **OTP codes never reach logs** — the SMS service logs masked numbers and
+  statuses only; `request-password-reset` always answers `{status:true}` so
+  it cannot be used as an account-existence oracle.
+
+The identity import endpoint's `invite` policy also supports phone-only rows
+when SMS is deliverable: the created account receives a **credential-free
+invitation SMS** and the employee completes first sign-in via phone OTP, then
+sets their own password.
+
 ---
 
 ## OAuth Providers