Summary

• Replace the dedicated app loading screen with inline preload states so the repositories UI can render immediately while initial data is still loading.
• Add placeholder detail and toolbar content for the new preload flow, including pending worktree creation/deletion states, so the detail pane no longer jumps between empty and loaded layouts.
• Preserve explicit worktree names during the first pending creation progress update, avoiding the regression where named worktrees briefly fall back to a generic "Creating…" label.
• Keep detail/toolbar precedence aligned for multi-selection so the multi-select summary does not show placeholder branch/open/run toolbar chrome when one selected row is still loading.

Test plan

• Launch the app while repositories are still loading and verify the repositories UI renders immediately with the inline preload placeholder instead of the removed dedicated loading screen.
• Select a pending or deleting worktree and verify the detail pane shows placeholder content and toolbar chrome only for the single-loading selection path.
• Create a worktree with an explicit branch name in a repo where local branch discovery is slow enough to expose the pending state, and verify the entered branch name stays visible throughout the initial progress updates.
• Cmd-click a second worktree while the primary selection is pending or deleting, and verify the detail pane switches to the multi-selection summary with no placeholder toolbar shown above it.
• Confirm the explicit-name regression remains covered by the targeted repository test and that the macOS app build still succeeds locally.