Add command contribution support for chat session view items

[Copilot]

This PR enables extensions to contribute commands to specific chat session view items in the Chat Sessions view. Extensions like the GitHub Pull Request extension can now register context-aware commands that appear as action bar items for individual session items.

Changes Made

1. New Context Keys

Added three new context keys in chatContextKeys.ts to provide session-specific context:

• chatSessionId: The unique ID of the session item
• chatSessionLabel: The display label of the session item
• chatSessionType: The type of session (e.g., 'local', 'github', etc.)

2. Enhanced SessionsRenderer

Modified the SessionsRenderer in chatSessions.ts to support menu contributions:

• Added menu service and context key service dependencies
• Enhanced template data with elementDisposable for proper cleanup
• Created context overlay for each session item using the new context keys
• Integrated action bar support with MenuId.ChatSessionsMenu
• Added proper disposal methods to prevent memory leaks

How Extensions Use This

Extensions can now contribute to the existing ChatSessionsMenu MenuId with context-aware commands:

{
  "contributes": {
    "menus": {
      "ChatSessionsMenu": [
        {
          "command": "github.createPullRequestFromSession",
          "when": "chatSessionType == 'github'",
          "group": "github",
          "order": 1
        }
      ]
    }
  }
}

Commands receive the full session object as an argument:

vscode.commands.registerCommand('github.createPullRequestFromSession', (session) => {
  // Access session.id, session.label, session.provider.chatSessionType
  console.log(`Creating PR for session: ${session.label}`);
});

Use Cases

This enables the GitHub Pull Request extension and other extensions to provide rich, session-specific functionality such as:

• Creating pull requests from chat session content
• Viewing associated PRs/issues
• Adding comments to linked items
• Quick management actions

The implementation follows VS Code's standard menu contribution patterns and provides a clean, extensible foundation for session-specific command contributions.

Warning

Firewall rules blocked me from connecting to one or more addresses

I tried to connect to the following addresses, but was blocked by firewall rules:

• electronjs.org
  • Triggering command: node-gyp (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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