LSP server crashes permanently disable language features for the session #13785

Problem

When an LSP server fails to spawn or crashes, it gets added to a broken set and is never retried during the session. This means if an LSP server temporarily fails (e.g., due to resource constraints or a transient error), the user loses LSP features for the entire session.

Expected behavior

Failed LSP servers should be retried with exponential backoff rather than permanently disabled. If a server recovers (e.g., resource pressure subsides), LSP features should resume.

Current behavior

broken: Set<string> marks failed servers permanently — no retry mechanism exists.