Expose negotiated MCP protocol version

[shusingh]

Summary

• Return mcpProtocolVersion from useConnection
• Pass the negotiated protocol version through App to the sidebar
• Show the protocol version in the connected server metadata when available
• Add hook coverage for reading mcp-protocol-version from response headers

Fixes #1324

Tests

• npm test -- --runTestsByPath src/lib/hooks/__tests__/useConnection.test.tsx --runInBand
• npm run lint in client
• npm run build in client
• npx prettier --check client/src/App.tsx client/src/components/Sidebar.tsx client/src/lib/hooks/useConnection.ts client/src/lib/hooks/__tests__/useConnection.test.tsx

[cliffhall]

Hi @shusingh

Sorry, the issue you referenced is against our v2/main branch, a totally different codebase. We're currently not accepting feature PRs for V1, only security and bug fixes.