### Feature: configurable default `top_k` for the `mcp_tool_search` virtual tool

**Version:** v1.92.0 (MCP Tool Search / `object_permission.mcp_tool_search_enabled`)

When a virtual key has `mcp_tool_search_enabled: true`, `/mcp` `tools/list` collapses the federated catalog to the two virtual tools `mcp_tool_search(query, top_k)` and `mcp_tool_call(tool_name, arguments)`. The `top_k` argument is **model-supplied per call and defaults to 5**, and there appears to be no way to configure that default.

**Problem:** with token-overlap ranking over a catalog of similarly-named tools, the correct tool frequently ranks 6–10 (families like `generate_image` / `get_image` / `view_image` tie on shared substrings). At the default `top_k=5` the target tool is silently omitted from search results, so the model can't call it — even though it's reachable. In our testing, recall was 0.70 @ k=5 and 1.00 @ k=10 on a ~113-tool catalog. The only way we found to get reliable recall is to instruct the model (via system prompt) to always pass `top_k=10`, which is brittle and client-specific.

**Request:** a server-side configurable default `top_k`, e.g. - per-key via `object_permission` (alongside `mcp_t…