CONF-014: Initialize-era versions listed in supportedVersions really work

Severity	Applies to	Spec section
warn	modern era, stdio, http	2026-07-28/server/discover#discoverresult

For every initialize-era revision (2025-11-25, 2025-06-18, 2025-03-26, 2024-11-05) that server/discover lists in supportedVersions, opens a fresh session and sends initialize with that version. Listing a version claims support for it, and a server that supports the requested version MUST answer with the same one (https://modelcontextprotocol.io/specification/2025-11-25/basic/lifecycle#version-negotiation). Shipped as warn because the spec does not spell out that supportedVersions covers initialize-era versions. Skipped when no such version is listed. Serving both eras concurrently on one endpoint is only a MAY (https://modelcontextprotocol.io/specification/2026-07-28/basic/versioning), so it is not checked.

From the command line: mcpprobe checks explain CONF-014. To leave it out of a run, add "CONF-014" to [checks] disable in mcpprobe.toml; to change how much it counts, use severity_overrides.