feat(mcp): pass the Kimi Code deferred MCP server key through

[dyoshikawa]

Summary

Kimi Code 0.43.0 added a per-server MCP key deferred: boolean that keeps a server's tools out of the model's top-level tool list until they are loaded on demand. toKimiCodeServer in src/features/mcp/kimi-code-mcp.ts emits a fixed allow-list of per-server keys, so deferred could not be authored from .rulesync/mcp.jsonc and was stripped from an existing .kimi-code/mcp.json on regenerate.

• Add deferred to the allow-list. Import already spreads unknown server keys into the canonical server, so the round trip now preserves it in both directions.
• Test: a generate + import round trip for a deferred: true server.
• Docs: deferred listed in the Kimi Code MCP note in docs/reference/file-formats.md; src/generated/docs-content.ts regenerated.

This is the mechanical MCP sub-gap recorded in the 2026-09-16 comment on the Kimi Code follow-up issue; the plugin-manifest target, the executor / runtime_id keys, the preserveKimiCodeRules forms and the dangerous_command_guard modeling remain open there.

Refs #2502

Evidence

• https://moonshotai.github.io/kimi-code/en/customization/mcp.html — server field table lists deferred (boolean, all transports) and the "Loading tools on demand" section.
• feat: declare dynamically_loaded_tools for official models and add per-server MCP deferred disclosure MoonshotAI/kimi-code#3667 — adds deferred: z.boolean().optional() to packages/agent-core-v2/src/mcpCore/config-schema.ts (merged 2026-09-14, shipped in 0.43.0).

Test plan

• pnpm cicheck green locally.

🤖 Generated with Claude Code

https://claude.ai/code/session_019yLN6CVqeZ8HCrjRb9o7mK

[dyoshikawa]

@dyoshikawa Thank you!