Add Swift Build Tool Plugin for automatic dependency validation

[tonyarnold]

• Implement DependencyAuditPlugin conforming to BuildToolPlugin protocol
• Plugin runs prebuild commands with target-specific analysis and Xcode output
• Update Package.swift with plugin target definition and capability
• Add documentation and examples for plugin usage

[Copilot]

Pull Request Overview

This PR adds a Swift Package Manager build tool plugin to automate dependency validation during package and Xcode builds.

• Implements DependencyAuditPlugin conforming to BuildToolPlugin to run the audit prebuild
• Updates Package.swift to declare the plugin product and target
• Adds documentation in README.md and notes in CHANGELOG.md for plugin usage

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
README.md	Added Build Tool Plugin integration documentation
Plugins/DependencyAuditPlugin/DependencyAuditPlugin.swift	Implemented plugin that runs a prebuild dependency audit
Package.swift	Added plugin product and target definitions
CHANGELOG.md	Updated changelog with plugin features and architecture

[Copilot]

[nitpick] Invoking the audit tool via swift run can be slower and less robust; consider using the PackagePlugin API (context.tool(named:)) to locate and execute the swift-dependency-audit executable directly.

Suggested change

	swift run swift-dependency-audit \\
	"\(try context.tool(named: "swift-dependency-audit").path)" \\

[Copilot]

[nitpick] Detecting test targets by checking the name substring is brittle; use the target’s type (e.g., TestTarget) or another metadata property to differentiate test and non-test targets.

Suggested change

	// Check if target name contains "Test" to identify test targets
	if !target.name.lowercased().contains("test") {
	// Check if the target is not a TestTarget to identify non-test targets
	if !(target is TestTarget) {

[Copilot]

[nitpick] Analyzing all targets can lead to unnecessary executions on non-source modules; consider filtering to SourceModuleTarget instances within shouldAnalyzeTarget to reduce overhead.

Suggested change

	// For now, analyze all targets and let the tool itself filter appropriately
	// The tool will skip targets that don't have source directories
	return true
	// Only analyze source-based targets
	return target is SourceModuleTarget