- Added `CompactionSummaryMessageOptions` interface to support optional fields and metadata in compaction summary messages.
- Included compaction method labels and before-after amount badge rendering in compaction views.
- Updated session maintenance and compaction methods to track and compute post-compaction token counts.
- Updated calls across agent and coding-agent packages to use the new compaction options object.
- Routed `customType: "handoff"` messages to the compact divider path in Agent Hub and UI helpers.
- Added handoff summary expansion that extracts context text and strips `<handoff-context>` wrappers.
- Refactored shared divider rendering into `SummaryDividerComponent` used by compaction and handoff messages.
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