fix: clear repo filter after creating worktree instead of auto-filtering

Previously, creating a worktree would auto-filter the sidebar to the
current repo, which could be confusing. Now clears the filter so all
worktrees remain visible, relying on revealWorktreeInSidebar to scroll
to the newly created worktree.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/renderer/src/components/sidebar/AddWorktreeDialog.tsx

@@ -128,7 +128,7 @@ const AddWorktreeDialog = React.memo(function AddWorktreeDialog() {
         setSidebarOpen(true)
         setSearchQuery('')
         setShowActiveOnly(false)
-        setFilterRepoId(repoId)
+        setFilterRepoId(null)
         setActiveWorktree(wt.id)
         revealWorktreeInSidebar(wt.id)
       }