fix(api): preserve full parent list in GitLogEntry

[XChen446]

Problem

\LogEntryOutputProcessor\ only keeps the first two parents (\mergeA/\mergeB): the parent edge is lost entirely for every single-parent commit (the fields are only assigned when there are 2+ parents), and octopus merges beyond the second parent are dropped. This breaks commit-graph reconstruction from \GitLogEntry\ (missing first-parent edges, missing octopus branches).

Verified on a full 5394-commit log dump: 3535 single-parent commits all produced empty parent fields.

Changes

• \GitLogEntry: add a \parents\ list carrying the full parent chain in git order; constructor backfills from \mergeA/\mergeB\ when \parents\ is null, so existing call sites keep working unchanged. New read-only \Parents\ property.
• \LogEntryOutputProcessor: collect all parent hashes during parsing instead of capping at two. \mergeA/\mergeB\ semantics are unchanged (first two parents for merges), so UI code checking \MergeA\ for merge detection is unaffected.
• Tests: single-parent commit (parents length 1, mergeA/B empty) and 3-parent octopus merge (all 3 parents preserved, mergeA/B = first two).

Impact

No breaking changes: binary-compatible field addition, optional constructor parameter, existing assertions (\AssertEqual) untouched.