Move all server matching logic to the extension/CLI side. The daemon no
longer calls pickServer() — it receives an explicit serverId (or
serverIds[] for diagnostics) and uses it directly for cache lookup and
server spawning.
Key changes:
- request op requires serverId: string
- diagnostics op requires serverIds: string[] — daemon fans out in
parallel via Promise.allSettled and returns grouped map
- formatDiagnostics() handles grouped results with per-server headers
when multiple servers contribute (single-server omits header)
- CLI picks servers locally before calling daemon helpers
- New pickDiagnosticServers() in extension returns all available,
non-disabled servers matching the file extension
This makes multi-server diagnostics (e.g., typescript-language-server +
oxlint) work naturally — the extension decides which servers to query,
the daemon just executes.
