fix(desktop-gpui): keep the timeline position when a new clip reloads the editor

[Zingzy]

Recording a new clip into an open project, or importing one from the Clips panel, sends the editor back to the start of the timeline. On a long project you lose your place every time you add a clip.

Cause

append_recorded_clip and the import path both finish with app_windows::reload_editor, which removes the editor window and opens a new one. The new EditorWindow starts with a default TimelineView, and its first render runs fit_on_mount, so the timeline opens at 0:00 like a fresh project. The old window's position and zoom are dropped with it.

Fix

• reload_editor reads the old window's Transform before removing it and hands it to the new window.
• The new window applies it at the first render, in place of fit_on_mount, through Transform::restored. That clamps the zoom and position to the new duration with the same update_zoom and set_position the timeline already uses.
• A view that was never fitted (zoom 0) is ignored and the window fits as before. Restoring it would clamp to MAX_ZOOM_IN.
• Only reload_editor sets the restore, so every other way of opening an editor is unchanged.
• The playhead and the sidebar tab still reset on reload. The playhead can only be sought once the playback engine is ready, which is after the first render, so this change keeps to the viewport.

The Tauri app in 0.6.0 behaves the same way. It isn't changed here.

Testing

• restored_transform_keeps_the_saved_view_and_clamps_to_the_timeline covers the saved view on a longer timeline, clamping to a shorter one, and the unfitted view.
• cargo test --bin cap-gpui: 1184 passed. cargo fmt --check passes, and cargo clippy --bin cap-gpui --tests reports nothing on the changed lines.
• Hand-tested in a debug GPUI build on macOS 26.4 (Apple M5) with a 40 s Studio project. I scrolled the timeline to 0:12.5 (17 s visible), opened Clips, chose Record a new clip, recorded the display for a few seconds and stopped:

Build	Timeline after the editor reopens
Cap 0.6.0 (Tauri)	back to 0:00
GPUI without this change	back to 0:00
GPUI with this change	stays at 0:12.5, same zoom, new clip appended (0:52 to 1:01)

Confidence Score: 5/5

The PR appears safe to merge; no blocking issues were found.

Summary

Keeps the timeline’s position and zoom when adding a clip reloads the GPUI editor.

• GPUI clip reloads keep the timeline at its current view.

No actionable issues found. Checks were limited to source inspection; tests and native UI checks were not run.

_{Reviews (2) · Last reviewed commit: "Merge branch 'main' into fix/editor-relo..." · Reviewed by Greptile}

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[richiemcilroy]

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