Implement Discord chat target

[Photon101]

Summary

• write a real Discord command/application manifest during build
• generate OAuth invite metadata with scopes and permissions
• sync global slash commands through Discord REST during real ship
• optionally patch the interactions endpoint and expose directory-review metadata
• add focused tests for manifest output, dry-run behavior, token guard, API calls, and API errors

Validation

• corepack pnpm exec vitest run packages/targets/chat-discord/src/index.test.ts
• corepack pnpm exec tsc -p packages/targets/chat-discord/tsconfig.json --noEmit
• corepack pnpm --filter @profullstack/sh1pt-target-chat-discord build
• git diff --check