Problem:
The fallback that tokenizes `eap->arg` by unescaped whitespace (when the
parser doesn't pre-split via `EX_EXPAND` etc.) lives in `nlua_do_ucmd`,
so only user-command callbacks got `eap.fargs`. Builtin commands routed
through `nlua_call_excmd` have to re-parse the args themselves
(e.g. `M.ex_lsp`).
Solution:
- Move the tokenization into `nlua_push_eap` so every Lua handler sees
`eap.fargs`. Keep only the `EX_NOSPC` override in `nlua_do_ucmd` (the
`nargs=1`/`?` case which is genuinely user-command-specific).
- Drop the re-parse in `M.ex_lsp`.
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