Keyboard shortcut for GitHub Copilot thinking effort in Configure Model

### Request

Add two commands "Increase Thinking Effort" and "Decrease Thinking Effort" to which we can bind to keys to quickly increase or reduce thinking effort during a GitHub Copilot chat.

### Discussion

Now that "Thinking Effort" and "Context Size" have been combined into a single selector, **it is extremely cumbersome to select the thinking effort using the keyboard**

* There seems to be no keyboard shortcut for selecting "Configure Model" in the chat.
* Once the "Configure Model" selector is open, the arrow keys moves the selection to two different categories.
* Pressing `` to select a new thinking effort does not close the selector, requiring an extra `` press.

### Summary

The "Configure Model" selector breaks Microsoft accessibility principles in several aspects. Allowing that selector to be bypassed with a direct change to thinking effort, bindable to a keypress, will mitigate some of the accessibility defects of that selector.

```
Version: 1.130.0 (user setup)
Commit: 1b6a188127eeaf9194f945eb6eb89a657e93c54c
Date: 2026-07-22T14:55:04Z
Electron: 42.6.0
ElectronBuildId: 14623276
Chromium: 148.0.7778.280
Node.js: 24.18.0
V8: 14.8.178.38-electron.0
OS: Windows_NT x64 10.0.26200
```