fix(autocomplete): apply the replacement range of matches given to the popup

[boogie]

Problem

Inserting a completion that carries a range throws when the popup was opened with a prepared list of matches:

var editor = ace.edit(el, {enableBasicAutocompletion: true, value: "abcdefGHI"});
editor.moveCursorTo(0, 3);
editor.execCommand("startAutocomplete", {
    matches: [{value: "xyz", range: new Range(0, 0, 0, 6)}]
});
// press Enter

TypeError: Cannot read properties of undefined (reading 'prefix')
    at CompletionProvider.insertMatch (src/autocomplete.js:889)

The options.matches branch of updateCompletions builds the CompletionProvider without an initial position, and insertMatch reads this.initialPosition.prefix when converting a completion's range into the span to replace. The completion never makes it into the document.

range is part of the completion API and is what language server integrations use to honour a textEdit, so this path is reachable for anyone feeding Ace prepared matches.

Change

Give the provider the position the popup was opened at.

The position is taken from the cursor rather than from the start of the selection. Ranges are applied as offsets around that reference point, and the regular completion path uses the cursor, so anchoring on the start of a non-empty selection would widen the replacement by the length of the selection. With the fix both paths agree:

	before	after
matches path, collapsed cursor	throws	replaces the range
matches path, non-empty selection	throws	replaces the range
regular path, collapsed cursor	replaces the range	unchanged
regular path, non-empty selection	replaces the range	unchanged

The range handling is also guarded on the initial position, since CompletionProvider is exported and can be constructed directly.

Out of scope, unchanged by this PR: ranges spanning more than one row are still ignored by the surrounding condition, on this path as on any other.

Test

test: replacement range of matches passed to execCommand is applied covers a range that extends on both sides of the cursor, and a non-empty selection that must not widen the replacement. Without the change the first case throws; anchoring on the selection start instead of the cursor fails the second with 'xyz' == 'xyzGHI'.

Open kitchen-sink @ a3e40f4ae27a7f0d62c253a4a0be8a2430a12be1