agent sessions - implement diff bar

[bpasero]

No description provided.

[Copilot]

Pull Request Overview

This PR refactors the diff statistics display in the agent sessions viewer by moving it from the renderer into a dedicated action view item. The change improves code organization by separating UI concerns and making the diff statistics interactive.

Key changes:

• Extracted diff statistics rendering logic from the renderer into a new AgentSessionShowDiffAction and AgentSessionDiffActionViewItem
• Replaced inline diff elements with an ActionBar-based toolbar
• Moved associated CSS styles from agentsessionsviewer.css to a new agentsessionsactions.css file

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
agentsessionsviewer.css	Removed inline diff styling and related color selectors, added padding for status element
agentsessionsactions.css	New file containing diff container styles and color definitions for files/additions/deletions
agentSessionsViewer.ts	Replaced inline diff elements with ActionBar toolbar integration and added action view item provider
agentSessionsActions.ts	New file implementing AgentSessionShowDiffAction and AgentSessionDiffActionViewItem for interactive diff statistics

[Copilot]

The session is retrieved twice unnecessarily. The session variable is already defined on line 81 but this.action.getSession() is called again to get the resource. Use session.resource instead.

Suggested change

	this.commandService.executeCommand(`agentSession.${session.provider.chatSessionType}.openChanges`, this.action.getSession().resource);
	this.commandService.executeCommand(`agentSession.${session.provider.chatSessionType}.openChanges`, session.resource);

[Copilot]

This logic duplicates the condition check from line 138 in agentSessionsViewer.ts. The action is only created when diff.files > 0 || diff.insertions > 0 || diff.deletions > 0, so these checks in the render method may be redundant. Consider simplifying to always display the values when the action exists, or document why the double-checking is necessary.

Suggested change

	elements.filesSpan.textContent = diff.files > 0 ? `${diff.files}` : '';
	elements.addedSpan.textContent = diff.insertions > 0 ? `+${diff.insertions}` : '';
	elements.removedSpan.textContent = diff.deletions > 0 ? `-${diff.deletions}` : '';
	elements.filesSpan.textContent = `${diff.files}`;
	elements.addedSpan.textContent = `+${diff.insertions}`;
	elements.removedSpan.textContent = `-${diff.deletions}`;