Measure GUI startup from the beginning of Run until the main view has loaded its store and is ready to build the History model.
Insert the measurement as the first in-memory History event using the existing RunRecord display path: Application / Started / Startup completed in <duration>. This keeps startup diagnostics visible in the UI without creating a separate application log file.
No scheduler, storage, or command log behavior is changed.
Replace the resizable HSplit on the Jobs tab with a border layout that keeps the job list pane at a stable minimum width.
The left pane now uses a small custom layout that asks Fyne for the content minimum size and applies at least 480 logical pixels. This prevents the divider from moving when the selected job changes while still allowing the toolbar buttons, including Delete, to fit when their calculated minimum width is larger.
Only the Jobs tab layout is changed; settings, storage, scheduler behavior, and documentation are intentionally left untouched.
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