Fix SchComponent.Comment not persisting through SchDoc/SchLib writers

[Andrei-Errapart]

Summary

SchComponent.Comment edits were silently dropped by both writers. SchDocReader populated Comment from DesignItemId instead of the child "Comment" parameter that SchLibReader correctly used, and neither writer ever pushed the property back into that parameter, so edits (and WithComment() on from-scratch components) had nowhere to go. SchDocWriter's byte-faithful replay path made this worse for loaded documents: it re-emits the exact bytes captured at read time whenever the primitive count is unchanged, swallowing even direct edits to the backing parameter's Value.

Changes

• SchDocReader/SchLibReader now derive Comment from the child "Comment" parameter once children are attached, recording a CommentAsRead baseline (internal) so the writers can tell an explicit edit from an untouched load.
• New SchLibWriter.SyncComponentComment pushes an edited Comment back into that parameter (creating one if absent); used by both writers.
• SchDocWriter disables its byte-faithful fast path only when a Comment edit is actually detected, so untouched documents still round-trip byte-identical.
• Regression tests in SchDocRoundTripTests/SchLibRoundTripTests covering mutate-after-load and from-scratch WithComment().

Test Plan

• Existing tests pass (dotnet test) — full suite at this commit: 854 passed, 0 failed, 10 skipped (pre-existing data-dependent skips, unrelated to this change)
• New tests added for new behavior — 4 new tests: SchDocRoundTripTests.WriteThenRead_ComponentComment_RoundTrips and WriteThenRead_RealFile_MutatedComment_Persists (real-file regression against the byte-replay path, using TestData/DAC.SchDoc), SchLibRoundTripTests.Component_Comment_RoundTrips and Component_MutatedComment_Persists

Checklist

• Code follows existing style and conventions
• Public API changes are documented with XML doc comments — no public API surface change: the two new members (SchComponent.CommentAsRead, SchLibWriter.SyncComponentComment) are internal, and both carry XML doc comments anyway
• No breaking changes (or clearly identified below) — no signature changes. One behavioral change, which is the fix itself: for .SchDoc reads, SchComponent.Comment now reports the child "Comment" parameter's value instead of DesignItemId whenever that parameter exists (matching SchLibReader and what Altium itself displays/persists). Code that relied on the old, incorrect value would observe the difference.

[Andrei-Errapart]

CI for this branch passed on my fork (same workflow, same base commit): https://github.com/Andrei-Errapart/AltiumSharp/actions/runs/32387331089