[Bug] MCP registration extensions not loaded on Linux

Environment

• OS: Ubuntu 24.04.4 LTS
• Eclipse Version: 2026-03 (4.39)
• Plugin Version: 0.20.0

Describe the bug
Create an Eclipse plugin with an extension registered for the "com.microsoft.copilot.eclipse.ui.mcpRegistration" extension point. The registered IMcpRegistrationProvider class is loaded and invoked as expected on both Windows and macOS but not on Linux. I've tested in several different environments with Ubuntu and have not been successful.

To Reproduce
Steps to reproduce the behavior:

1. Start an Eclipse instance with a plugin registering an IMcpRegistrationProvider.
2. Open the Copilot preferences to confirm no MCP server from the plugin was registered, requesting approval.
3. Note the following warning in the Eclipse Error Log which looks related (I'll explain more below):

!ENTRY org.eclipse.lsp4e 2 0 2026-07-23 09:49:49.451
!MESSAGE [LS:GitHub Copilot Language Server][Warning]	[default] Policy watcher not available - continuing without policy watching: Unsupported platform

Expected behavior
The MCP server contributed by the plugin should be registered as it is on Windows and macOS.

Additional context

I spent some time investigating this. The class McpExtensionPointManager checks the boolean mcpContributionPointEnabled which defaults to false. The only place where I see it possibly being set to true is from CopilotLanguageClient.onDidChangePolicy(DidChangePolicyParams) which I confirmed is never getting called. This "policy/didChange" call back from the Copilot Language Server is never happening on Linux. I suspect this may be related to the "Policy watcher not available - continuing without policy watching: Unsupported platform" in the Eclipse Error Log since they both sound policy-related.

If this is really a problem with the Copilot Language Server and not the Eclipse plugin then I'd be happy to file this bug report in the appropriate place for that.

I would also appreciate any workaround anyone could share if possible to make this work on Linux, like if I'm just missing some extra system package that's preventing this from working (or something like that).

Start with McpExtensionPointManager and CopilotLanguageClient.onDidChangePolicy(DidChangePolicyParams), then reproduce on Ubuntu and inspect the Eclipse Error Log for the policy watcher warning. Compare the Linux behavior with Windows or macOS, and determine whether the missing policy callback is in the Eclipse plugin or Copilot Language Server. Done means the contributed MCP server registers on Linux or the issue is clearly handed to the appropriate upstream project.