ci: pin checkout in manual strategy switch (#197)

Pins the Manual Strategy Switch checkout action to the verified v6.1.0 commit.

Author: Pigbibi

.github/workflows/manual-strategy-switch.yml

@@ -181,7 +181,7 @@ jobs:
       RUNTIME_SETTINGS_BINANCE_REPO: ${{ vars.RUNTIME_SETTINGS_BINANCE_REPO }}
     steps:
       - name: Checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@d23441a48e516b6c34aea4fa41551a30e30af803 # v6.1.0
 
       - name: Enforce write safety gates
         run: |