feat(startup): enable startup clone requests from CLI and IPC

Adds startup clone support with a new clone request type and parsing.
It wires a CLI and IPC pathway to forward a clone to a running app.
UI and docs were updated to reflect startup clone behavior.

- Introduce StartupCloneRequest and argument parsing.
- Wire IPC to pass clone requests and clone on startup.
- UI updated to queue clone requests and trigger clone.

src/lib/components/LinePatchDialog.svelte

@@ -277,7 +277,7 @@
         <span class="eyebrow">{scopeLabel}</span>
         <p class="dialog-title" title={displayPath}>{displayPath}</p>
       </div>
-      <div class="dialog-header-actions">
+      <div class="dialog-header-actions line-patch-header-actions">
         <div class="tool-surface-choice" aria-label={isGerman ? "Diff öffnen mit" : "Open diff with"}>
           <span>{isGerman ? "Öffnen mit" : "Open with"}</span>
           <button class="active" type="button" aria-pressed="true" title={isGerman ? "In Gitty anzeigen" : "Show in Gitty"}>