Add unsorted expected completions

[gabritto]

Adds the unsorted option to expected completion lists in fourslash, and correspondingly in the conversion script.
15 new tests, 5 of which are skipped due to failing.

[Copilot]

Pull Request Overview

This PR introduces support for an Unsorted completion expectation in Fourslash tests and updates the conversion script to both parse and generate code for the new unsorted property.

• Adds a new Unsorted []CompletionsExpectedItem field and verification path in internal/fourslash/fourslash.go
• Imports maps and slices for unsorted-item handling
• Updates convertFourslash.mts to recognize, parse, and emit the unsorted argument
• Adds 15 new Fourslash test files using Unsorted (5 are skipped due to current failures)

Reviewed Changes

Copilot reviewed 18 out of 18 changed files in this pull request and generated no comments.

File	Description
internal/fourslash/fourslash.go	Added Unsorted field and its verification logic
internal/fourslash/_scripts/convertFourslash.mts	Parses and generates the unsorted property in conversion script
internal/fourslash/_scripts/failingTests.txt	Marks newly added tests (with Unsorted) as failing/skipped
internal/fourslash/tests/gen/*	New Fourslash tests exercising the Unsorted option

Comments suppressed due to low confidence (1)

internal/fourslash/_scripts/convertFourslash.mts:392

• Make this fallback branch explicit for unsorted only (e.g. else if (propName === "unsorted")) and add a default case afterward to throw an error on unknown properties instead of silently treating them as unsorted.

                else {