Surface negotiated protocolVersion through useInspectorClient

[cliffhall]

Background

useInspectorClient returns status, capabilities, serverInfo, instructions — but not the protocolVersion the InspectorClient negotiated with the server. The MCP InitializeResult includes protocolVersion as a top-level field.

#1244's App.tsx builds an InitializeResult for InspectorView's connected header by hard-coding protocolVersion: "2025-06-18" since the hook doesn't expose the real value. That's a placeholder; the connected header doesn't read protocolVersion today, but as soon as anything wants to display "MCP 2025-06-18 over stdio" the hard-code becomes a bug.

Scope

• Add protocolVersion?: string to UseInspectorClientResult in core/react/useInspectorClient.ts.
• Track it via the existing serverInfoChange / capabilitiesChange event family, or add a dedicated protocolVersionChange event to InspectorClientEventMap if it can land independently of capabilities.
• Update App.tsx (#1244) to read the value from the hook and drop the hard-coded "2025-06-18".

Out of scope

• Negotiation strategy / version compatibility checks — separate concern.

Related

• Wire App.tsx to v2 core/ hook layer; remove demo stub from InspectorView #1244 — has the hard-code at App.tsx, with a comment pointing here.