LabelAnalysis gains `chapter_summary: Vec<ChapterSummary>` — one row
per .mpls file in /BDMV/PLAYLIST/, with chapter count (PlaylistMark
entries with mark_type ≤ 1) and approximate playlist duration in
seconds. Sorted by playlist filename.
Sourced from the existing crate::mpls parser (no new format work).
Useful for identifying the main feature playlist at a glance — it's
the one with the longest duration. Verified on disc-11 (Dune Pt 2):
00800.mpls correctly identified as 2h 45m 49s with 18 chapters
amid 30+ shorter playlists.
Doesn't touch the per-title `disc::DiscTitle::chapters` field which
disc::bluray.rs already populates from the same marks during disc
init — this is purely the diagnostic surface for labels-analyze.
MattJackson
a876ce846b