Passing empty array to displayFindings doesn't clear the Code Issues pane

## Problem
There is no way to manually clear the Code Issues pane. In a large codebase, this becomes a problem as I only want to see the issues in an isolated chunk of code.

I've asked Claude to clear the Code Issues pane. It comes back saying "cleared" but the issues remain in the pane. I've then asked it to figure out why they haven't been cleared and it told me that passing in [] to the `displayFindings` tool does not seem to work.

## Steps to reproduce the issue
1. Ask it to review a chunk of code and populate the Code Issues pane
2. Ask it to clear the Code Issues pane (it should respond with something along the lines of "Code Issues pane has been cleared")

## Expected behavior
The code issues pane should be cleared by Claude, or at the very least there should be a manual way of clearing the pane.

## System details (run `AWS: About` and/or `Amazon Q: About`)
- OS: Win
- Visual Studio Code version: 1.106
- Amazon Q version: 1.104

Start by tracing the displayFindings tool entry point and the Code Issues pane behavior when it receives an empty array. Reproduce the reported flow in VS Code with Amazon Q, then verify that passing [] clears existing findings or that a documented manual clearing path is available.

Written by the indexing model from the issue text.