fix: Persist editor scroll position and cursor location across workspace switches

[Cheezeiii365]

Summary

When switching between workspaces and back, editor panes should restore to the exact scroll position and cursor location they were at before the switch.

Current Behavior

Scroll position and/or cursor location is lost when switching workspaces and returning.

Expected Behavior

• Cursor line and column restored exactly
• Scroll offset (viewport top line) restored exactly
• Should work for all open editor tabs, not just the active one

Notes

TabState already stores cursor position — this may be a matter of ensuring scroll offset is also captured and that restoration timing is correct (CodeMirror may need to be fully rendered before scroll can be set).