feat: add workspace state and plugin communication

[DongyuZhao]

Summary

• introduce CodeCanvasStore and CodeCanvasWorkspace for managing canvas state
• connect bench and canvas via environment objects to allow plugins to open workspaces
• extend example benches with simple file and trace interactions

Testing

• swift test

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https://chatgpt.com/codex/tasks/task_e_6897069f9a78832290ca438b4a6c7883

[Copilot]

Pull Request Overview

This PR adds workspace state management and plugin communication to the CodeCanvas framework. It introduces a centralized store for managing canvas workspaces and enables bench components to open workspaces through environment objects.

• Adds CodeCanvasStore and CodeCanvasWorkspace protocol for managing workspace state
• Connects bench components to canvas via environment objects for plugin communication
• Updates example benches with interactive file and trace functionality

Reviewed Changes

Copilot reviewed 9 out of 10 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
CodeEditorExtension.swift	Adds file editor workspace and interactive file collection with store integration
ClientRestfulExtension.swift	Adds REST client workspace and interactive trace collection with store integration
CodeSpaceContainer.swift	Updates to display workspace content from store when available
CodeBenchContainer.swift	Adds store environment object and clears workspace on bench selection
CodeCanvasShell.swift	Creates and provides store as environment object to child views
CodeCanvasStore.swift	New store class for managing workspace state with open/clear methods
CodeCanvasWorkspace.swift	New protocol defining workspace interface with content view method
CodeCanvasFile.swift	Makes file model conform to Identifiable protocol
CodeCanvasExtension.swift	Adds SwiftUI import guard for consistency

[Copilot]

The workspace property should be private(set) to prevent external modification and maintain encapsulation. External code should only be able to modify the workspace through the open() and clear() methods.

Suggested change

	@Published public var workspace: (any CodeCanvasWorkspace)?
	@Published public private(set) var workspace: (any CodeCanvasWorkspace)?