chore(ci): call the auto-merge sweep from bitbaum/fleet

The fleet automation moved out of dotfiles on 2026-08-28; the dotfiles path
is now a forwarding shim. This points the caller at the sweep's real home.
One line; the reusable workflow's interface is unchanged.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AZCNYHwjEeqxNpYCUk6Yna

Author: catomean

.github/workflows/auto-merge.yml

@@ -39,7 +39,7 @@ permissions:
 
 jobs:
   sweep:
-    uses: bitbaum/dotfiles/.github/workflows/auto-merge-sweep.yml@master
+    uses: bitbaum/fleet/.github/workflows/auto-merge-sweep.yml@main
     with:
       base_branch: main
       ci_workflow: ci.yml