Fix Swift label highlight captures

[ollieatkinson]

Summary

Fix Swift Tree-sitter highlight captures so function parameter labels/names and call argument labels are not classified as @property.

This keeps themes from having to style Swift labels the same way as real member properties.

Fixes #74.

Test Case

The issue screenshots include this representative Swift code:

@discardableResult
func printSummary(for jobs: [BuildJob]) -> Int {
    let completed = jobs.filter { $0.state == .finished }
    let grouped = Dictionary(grouping: jobs, by: \.state)
    return completed.count
}

Expected captures after this change:

for      -> @variable.parameter
jobs     -> @variable.parameter
grouping -> @label
by       -> @label
filter   -> @function.call

Before this change, for, jobs, grouping, and by were captured as @property.

Validation

• Ran tree-sitter-cli query against the screenshot-derived Swift snippet and compared origin/main vs this branch.
• Confirmed the captures changed from @property to @variable.parameter / @label for the issue cases.
• Confirmed nearby jobs.filter remains captured as @function.call.
• Ran cargo test.
• Ran git diff --check.

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[ollieatkinson]

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