Prove editor diagnostics and hover

Parent

#10 — Add cross-platform VS Code editor adapter for MrBuild LSP proof

What to build

Use the shared fixture and real Coordinator session to prove that standard editor diagnostics and hover results reach the VS Code surface through the Language Workers.

Acceptance criteria

• Opening the fixture displays the intentional diagnostic in the editor diagnostics UI.
• The diagnostic is produced by the real LSP/worker path and not by adapter-local logic.
• Hovering a known F# symbol returns a visible hover result.
• Hovering a known C# symbol returns a visible hover result.
• The proof tolerates normal editor document-open and synchronization timing without fixed sleeps as its only readiness mechanism.
• The acceptance test fails when the Coordinator or relevant worker is not serving the request.

Blocked by

• #13 — Add the shared fixture and isolated VS Code proof launcher

Start with the shared fixture and isolated VS Code proof launcher from #13, then trace the Coordinator and Language Workers used by the acceptance test. Verify diagnostics and hover results through the real editor surface, using readiness based on document synchronization rather than fixed sleeps. Done means the test observes the intentional diagnostic and visible F# and C# hover results, and fails when the Coordinator or worker is unavailable.