Cursor runs get no MCP injection: memory, orchestration, preview, spec/teach all dead — and prompts advertise the missing tools #700

Found in a full provider-feature audit. Cursor is the only major provider with no MCP injection hook at all:

• memory-sup.js has provider hooks for claude (getClaudeMcpArgs :316), codex (:395/:463), kimi (ensureKimiMcpConfig/:595), and grok (ensureGrokMcpConfig :1078) — zero cursor matches.
• startCursorRun builds args from buildArgs + the pin-task plugin only (electron/runner.js:4771-4791); cursor buildArgs passes --approve-mcps but no config (electron/providers.js:944-971).
• registerMcpServer refreshes claude/kimi/grok configs only (memory-sup.js:184-205); nothing ever writes ~/.cursor/mcp.json (mcpImports only reads it as an import source, mcpImports.js:38).

Consequences for cursor threads: no coder-memory tools, no coder-threads (thread_fork, task list, peer_send, thread_merge/pr, ask_user, work_suggest, spec_submit, teach_review), no browser preview, no user-imported MCP servers. Spec-driven cursor threads deadlock (agent cannot call spec_submit, gate never opens, services.js:2441-2463); teach mode never advances (teach_review unreachable).

Worse, it's silently misleading: prompt notes advertising those tools (selfIdNoteFor/subagentPoolNoteFor/specNoteFor, services.js:795-827,2791-2800) are gated only on the server being globally registered, so a cursor lead is told to orchestrate with tools it never received.

The fix mechanism exists in-tree: cursor supports --plugin-dir (already used for the pin-task hook) and reads .cursor/mcp.json.