Fix publish layout sync false positives

[akhilles]

Note

Low Risk
Narrowly scoped normalization around file comparisons and .kicad_pro output formatting; main risk is potentially missing a meaningful change if it only differs by trailing whitespace.

Overview
Reduces layout.sync false positives during pcb publish/--check by treating synced KiCad layout files as equal when they only differ in trailing whitespace.

This changes pcb-layout's drift detection to compare file contents after trimming ASCII whitespace at EOF, and updates pcb release’s .kicad_pro writer to always end the pretty-printed JSON with a newline. Targeted unit tests were added for both behaviors, and the fix is documented in the changelog.

^{Written by Cursor Bugbot for commit d70f0d6. This will update automatically on new commits. Configure here.}