Fix: Incorrect treatment of the model's table as missing when processing batches with index > 0

[izeigerman]

Fixes #5555

[Copilot]

Pull Request Overview

This PR fixes a bug where batches after the first batch (index > 0) incorrectly treated the model's target table as missing, causing the 'creating' runtime stage to execute multiple times instead of just once.

Key Changes:

• Added logic to correctly determine target table existence for batches with index > 0
• Added test case to verify the 'creating' stage only executes for the first batch

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
sqlmesh/core/scheduler.py	Fixed target table existence check to account for batch index
tests/core/integration/test_change_scenarios.py	Added test case verifying 'creating' stage executes only once across multiple batches

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}