When a server supports both document and workspace pull diagnostics,
`on_refresh` only dispatched a `workspace/diagnostic` request. The
workspace response handler skips buffers with `pull_kind == "document"`
(i.e. all buffers opened by the user), so their diagnostics went stale
until the next `didChange` or `didOpen` event.
Change `on_refresh` to always refresh document-pull buffers via
`textDocument/diagnostic`, regardless of whether the server also
supports workspace diagnostics. This ensures that opened buffers
see updated diagnostics (e.g. after a save triggers an external
tool like PHPStan) without requiring the user to re-enter insert
mode.
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