fix: commands not executing when chat hasn't been opened

Description

The duo chat commands were running before the chat was fully initialized. Updated the show method for the duo_chat_controller to wait for the chat to be ready, when chat has not previously been opened.

Related Issues

Resolves #953

How has this been tested?

1. Use this merge request on the VS code extension
2. Run the LS and VS code (test on both desktop and webIDE)
3. Run any duo chat command from the menu (do not open the chat initially)
4. After chat opens and initializes, the command should be run

• If src/browser or src/common has been modified, please consider interoperability with the Web IDE. See Running the Extension in WebIDE.
• Consider an end-to-end test for significant new features that aren't covered by integration tests.

Screenshots (if appropriate)

Testing Commands

What CHANGELOG entry will this MR create?

• fix: Bug fix fixes - a user-facing issue in production - included in changelog
• feature: New feature - a user-facing change which adds functionality - included in changelog
• BREAKING CHANGE: (fix or feature that would cause existing functionality to change) - should bump major version, mentioned in the changelog
• None - other non-user-facing changes

Closes #953