[Bug]: Slow-speed clips are not fully visible on the timeline

[meiiie]

Split from #242 after a current follow-up from @FBox467.

Description

The reporter says that in v1.2.1, after lowering playback speed, the whole clip is no longer visible on the timeline.

This maps to the original #242 timeline-speed item: after changing clip speed, the displayed duration and the clip block's appearance on the timeline should update so the clip remains reachable and visually understandable.

Expected Behavior

When a clip is slowed down, the timeline should reflect the longer effective duration and keep the full clip visible or reachable through the timeline scroll/zoom controls.

Current Signal

• OS/build from the original report: Windows 10, previously v1.1.23
• Current follow-up: reporter mentions v1.2.1
• Trigger: lower playback speed on a clip
• Symptom: the entire clip is not visible on the timeline

Scope

This issue tracks the slow-speed timeline visibility/layout regression only. The broad #242 omnibus remains closed so each confirmed current issue can be fixed and verified independently.

[FBox467]

[meiiie]

Opened PR #454 to fix this: #454

The fix derives the timeline range from the furthest clip end while keeping the original source duration as the floor, so slow-speed clips remain fully visible/reachable without shrinking the base timeline for fast-speed clips.