Register a completer for a single (reference, argumentName) pair, so a
consumer no longer hand-routes every completable argument inside one global
setCompletionRequestHandler delegate. The delegate receives the partial
value typed so far and returns the candidate completions; the server wraps
them in a CompleteResult (use CompleteResult.prefixMatch for the common
prefix-matching case). Declaring any completer advertises the completions
capability. completion/complete dispatch tries the global handler first
(when set) and falls back to a matching per-argument completer, then to an
empty CompleteResult.
Register a completer for a single (reference, argumentName) pair, so a consumer no longer hand-routes every completable argument inside one global setCompletionRequestHandler delegate. The delegate receives the partial value typed so far and returns the candidate completions; the server wraps them in a CompleteResult (use CompleteResult.prefixMatch for the common prefix-matching case). Declaring any completer advertises the completions capability. completion/complete dispatch tries the global handler first (when set) and falls back to a matching per-argument completer, then to an empty CompleteResult.