[Bug]: Merge Output $Action reported as Invalid Column

### Description

I have several Stored Procedures that contain Merge statements. I have recently installed VS Code with the MSSQL extension. When I open any of these Stored Procedures, the Output $Action is identified as an invalid column.

This is similar to Issue: #20411

The Merge statement is in a Stored Procedure, wrapped inside a Try/Catch block

### Steps to Reproduce

1. Connect to db
2. Open stored procedure containing a Merge statement with Output $Action clause
3. Parser identifies $Action as an invalid column

### Affected Area

- [ ] Connection dialog (SQL Server | Azure browse/Fabric browse)
- [x] Query editor
- [ ] 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 affected area

_No response_

### Environment Information

VS Code: 1.125.1
MSSQL: 1.43.0
Windows: 11

### Confirmation

- [x] I have searched existing issues and couldn't find a match
- [ ] I want to work on this issue

Reproduce the report in the query editor with a stored procedure containing a MERGE statement, an OUTPUT $Action clause, and a TRY/CATCH block. Confirm that the parser reports $Action as an invalid column, then trace the query-editor parser behavior until the diagnostic is no longer reported for this statement.

Written by the indexing model from the issue text.