input: Fix ghost first line suffix y offset

[zanmato]

Description

When using inline completions (ghost lines), the first line suffix is not aligned with the rest of the line. This changes it to capture the current cursor row y instead of using the cursor bounds for the y offset.

Screenshot

Before	After

Comparison

How to Test

1. cargo run --release --example editor
2. Type fn ( to get inline completions

Checklist

• I have read the CONTRIBUTING document and followed the guidelines.
• Reviewed the changes in this PR and confirmed AI generated code (If any) is accurate.
• Passed cargo run for story tests related to the changes.
• Tested macOS, Windows and Linux platforms performance (if the change is platform-specific)