feat: add Cursor harness integration

[oxwen11]

Summary

• add a Cursor ACP harness with executable discovery, JSON-RPC transport, authentication, model selection, session lifecycle, permissions, and streaming update transforms
• register cursor across the shared contract, server runtime, harness capabilities, and chat UI
• document the ACP integration decision and add focused transport, transform, executable, and agent tests

Testing

• pnpm lint:check
• pnpm format:check
• pnpm exec turbo run test --filter=@vibest/server --force -- test/harness/cursor test/harness/adapter-capabilities.test.ts (27 tests passed)

Known baseline/environment failures

• pnpm check reaches typecheck but fails on the existing apps/app/src/features/chat/runtime/chat-update.test.ts:421 fixture missing OutgoingMessage.delivery; the same line is present on the base commit and current origin/main
• the full forced test suite passes the Cursor tests but has one environment-dependent PTY spawn failure in packages/server/test/rpc-pty.test.ts

[github-actions]

React Doctor found 1 issue in 1 file · 1 warning · score 92 / 100 (Great) · full project

1 warning

src/features/chat/runtime/client-prompt-queue.ts

• ⚠️ L0 unused-file

_{Reviewed by React Doctor for commit 7f02509. See inline comments for fixes.}