Avoid allocations when checking project reference declaration directories

[auvred]

Fixes #63976

ContainsPath does the same check without extra allocations

TypeScript/tsc/internal/tspath/path.go

Lines 1085 to 1093 in e9e4774

	// ContainsPath checks whether child is contained within or equal to p.
	// Since Path values are already rooted, reduced, and case-canonicalized,
	// this is a simple string prefix check.
	func (p Path) ContainsPath(child Path) bool {
	if len(p) == 0 {
	return false
	}
	return p == child || len(child) > len(p) && strings.HasPrefix(string(child), string(p)) && (p[len(p)-1] == '/' || child[len(p)] == '/')
	}

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Before: handled method 'textDocument/references' (32) in 3.071585458s

After: handled method 'textDocument/references' (20) in 2.692099625s

[Copilot]

Pull request overview

Replaces allocation-heavy path concatenation with Path.ContainsPath when checking project-reference declaration directories.

Changes:

• Uses canonical path containment checks in both directions.
• Avoids ephemeral string allocations in a language-server hot path.

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