Remove nested push from template expansion

[luojiyin1987]

Summary

The expandTemplate function contains a nested Array.push call.

The inner push adds the file marker and returns the new array length.
The outer push then adds that number to the parts array.

The assemble function ignores non-string values.
The extra number does not normally change generated output.
The current structure is still incorrect and obscures the intended item order.

Proposed scope

• Add the file marker directly to the outer push call.
• Keep the marker, banner, and file content order unchanged.
• Keep all generated output unchanged.

Validation

A temporary source transformation generated all seven ublock templates before and after the change.
Every generated file was byte-identical.
The comparison covered about 3.4 MB of generated data.