fix(postprocess): suppress single-child wrappers with trailing delimiters

[HarshK97]

Problem

1. When a single-child statement (like an assignment or call ending with a semicolon) moves, suppressCoextensiveWrappers required an exact EndByte match before suppressing the parent wrapper.
2. Because the statement wrapper includes the semicolon and the child expression doesn't, parent.EndByte was always larger than node.EndByte. So the wrapper was never suppressed, leaving phantom insert and delete boxes around lines that just moved.

What Changed

• Relaxed the check in suppressCoextensiveWrappers so single-child and scaffolding wrappers get suppressed if they share StartByte with the child, without needing exact EndByte equality.
• Updated internal/postprocess/collapsing_test.go to verify that statement wrappers with trailing semicolons are properly dropped when their child moves.
• Updated golden actions and UI fixtures for 5 Zig test cases where statement wrappers were previously surviving.