[Feature Request]: Copy Headers with brackets

### Feature Description

When Copy Headers is clicked in a table, it could be helpful if the copy had brackets around it. For example, if a column name is "case" then selecting Copy Headers could add "[case]" the clipboard.

### Problem and Motivation

I often copy a header and then paste it in my code. Sometimes a header is a sql key word. In such a case, I need to add in the backets myself to prevent errors. It would be convenient to not have to add in the brackets.

### Related Area

- [ ] Connection dialog (SQL Server | Azure browse/Fabric browse)
- [ ] Query editor
- [x] Query results panel
- [ ] Object Explorer
- [ ] GitHub Copilot integration
- [ ] Preview/Edit data
- [ ] Table Designer
- [ ] Schema Designer
- [ ] Schema Compare
- [ ] Local SQL Server Container provisioning
- [ ] SQL database in Fabric provisioning
- [ ] DACPAC/BACPAC export/import
- [ ] SQL Database projects
- [ ] Query Plan Visualizer
- [ ] Other (please describe below)

### If you selected "Other", please describe the area

_No response_

### Confirmation

- [x] I have searched existing feature requests and couldn't find a match
- [ ] I want to help implement this feature

Start by locating the Query results panel implementation and its Copy Headers action in the vscode-mssql extension. Trace how selected column names are placed on the clipboard, then check nearby tests if available. Done means copied headers include brackets around each column name, including names such as "case".

Written by the indexing model from the issue text.