[Bug]: headless-360 discover with resultType "endpoint" returns only workflow results, never endpoints

### Summary

`discover` accepts a `resultType` of `endpoint`, but every result it returns is a workflow (`sor_type: "workflow"`). No endpoint-kind result has ever come back, across 18 themed queries on two separate dates.

### Environment

Production org (Enterprise Edition), API v67. Client: Claude Code via a pre-registered External Client App (public client, PKCE, `mcp_api` scope). Server reports `headless-360 1.0.0`. Observed 2026-08-22 across 18 `discover` queries, re-confirmed 2026-08-28.

### Detail

16 themed queries on 2026-08-22 surfaced 192 distinct multi-step recipes and zero individual endpoints. Re-running three of those queries verbatim on 2026-08-28 (MCP registry, SOQL-as-endpoint, user management) returned the same counts with shifted id sets, and still no endpoint-kind results. Setting `resultType: "endpoint"` explicitly does not change the kind of result returned; it appears only to filter, and on the endpoint-filtered query the newly added top-level `filtered_out_count` came back as 3 while the surviving results were still all workflows.

### Why this matters

`discover` reads as an index over the platform's operations, and `resultType: "endpoint"` reads as the way to find a specific API rather than a multi-step recipe. In practice it is a recipe library only. An agent looking for "the endpoint that does X" gets a 50-step onboarding workflow instead, then either follows the whole recipe or gives up. The recipes themselves are genuinely good, so this is about discoverability, not quality.

### Suggested resolution

Either return endpoint-kind results for `resultType: "endpoint"`, or drop the parameter and say plainly in the tool description that `discover` indexes recipes rather than individual endpoints.

Start at the discover entry point and reproduce the reported queries with resultType set to "endpoint," checking whether returned results have sor_type "endpoint" or "workflow." Done means the parameter either returns endpoint-kind results as described, or its behavior and purpose are made explicit in the tool description; the payload names no files or tests.

Written by the indexing model from the issue text.