feat: add discord service emulator

[mvanhorn]

Summary

Adds a Discord service emulator with stateful guilds, channels, members, roles, and messages, plus full OAuth 2.0 (authorization code flow) and a Message / Guild Inspector. Snowflake IDs match Discord's documented 64-bit format. Both Authorization: Bot <token> and Authorization: Bearer <token> are supported.

Closes the OAuth + REST surface — interactions / signature verification, guild webhooks, and Gateway WebSocket are intentionally separate follow-ups.

Why this matters

Discord has become the community plane for most modern SaaS — community bots, role automation, slash-command integrations, magic-link sign-ins through Discord OAuth. The official discord.js SDK has ~700K weekly npm downloads and @discordjs/rest is in every modern bot stack. CI tests against Discord today either hit production (rate limits, real users, real channels) or stub at the HTTP level. No general-purpose emulator covers Discord — WireMock is too low-level and MSW is browser-only.

emulate's Store gives us stateful guilds + channels + messages; the shared OAuth helpers give us a real authorization_code + Bearer/Bot token flow.

Inspector

Browse seeded guilds, channels, messages, members, and roles. Tabbed navigation, terminal-green aesthetic from core/src/ui.ts.

OAuth Consent

Standard /oauth2/authorize flow with a user picker.

Discord API Coverage

Method	Description
GET /api/v10/users/@me	Authenticated user (Bot or Bearer)
GET /api/v10/guilds / POST	List and create guilds
GET /api/v10/guilds/:id	Get guild
PATCH /api/v10/guilds/:id / DELETE	Update / delete guild
GET /api/v10/guilds/:id/channels / POST	List / create channels
GET /api/v10/channels/:id / PATCH / DELETE	Channel CRUD
GET /api/v10/channels/:id/messages / POST	List / send messages
GET /api/v10/channels/:id/messages/:id / PATCH / DELETE	Message CRUD
GET /api/v10/guilds/:id/members	List members
PUT /api/v10/guilds/:id/members/:userId	Add member
PATCH /api/v10/guilds/:id/members/:userId / DELETE	Update / remove member
GET /api/v10/guilds/:id/roles / POST	List / create roles
PATCH /api/v10/guilds/:id/roles/:roleId / DELETE	Role CRUD
GET /oauth2/authorize	OAuth consent page (Universal Login style)
POST /api/oauth2/token	OAuth token exchange (authorization_code)

Bot tokens

Configure applications in seed config; bot tokens auto-register with the emulator's tokenMap so Authorization: Bot <token> works immediately:

discord:
  applications:
    - id: "123456789012345678"
      client_id: discord-client-id
      client_secret: discord-client-secret
      name: My Discord Bot
      bot_token: discord-bot-token
      redirect_uris: [http://localhost:3000/api/auth/callback/discord]
  users:
    - id: "222222222222222222"
      username: developer
      email: dev@example.com
  guilds:
    - id: "333333333333333333"
      name: My Server
      members:
        - { user_id: "222222222222222222", roles: ["444444444444444444"] }
      roles:
        - { id: "444444444444444444", name: admin, permissions: "8" }
      channels:
        - { id: "555555555555555555", name: general, type: GUILD_TEXT }

Default port

4012 (appended at the end of SERVICE_NAME_LIST after clerk — no other service's port shifts).

What's not yet covered

• Slash commands + interactions HTTP callback with Ed25519 signature verification (separate PR)
• Guild webhooks via WebhookDispatcher (separate PR)
• Gateway WebSocket — most modern Discord bots have migrated to interactions-over-HTTP, so deferring this keeps the diff focused

Tests

35 Vitest tests covering guild / channel / message / member / role CRUD, OAuth code flow, snowflake bit layout, both auth header shapes (Bot and Bearer), inspector rendering, and seed-config token registration.

pnpm --filter @emulators/discord test    # 35 passed
pnpm --filter @emulators/discord build   # passes
pnpm --filter emulate build              # registry integration verified
pnpm format:check                        # passes
pnpm lint                                # passes

[vercel]

@mvanhorn is attempting to deploy a commit to the Vercel Labs Team on Vercel.

A member of the Team first needs to authorize it.