Fix checkout target for pull request workflows (#212)

when using `pull_request_target:` the default ref is main so all checks
are run from the main branch rather than the PR. This re-targets all
checkouts to a generated `merge_commit` which matches the behavior of
`pull_request:`. ([ref](actions/checkout#518))

Signed-off-by: dalthecow <[email protected]>

Author: sjmonson

.github/workflows/development.yml

@@ -12,6 +12,8 @@ jobs:
         python: ["3.9", "3.13"]
     steps:
       - uses: actions/checkout@v4
+        with:
+          ref: "${{ github.event.pull_request.merge_commit_sha }}"
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
@@ -47,6 +49,8 @@ jobs:
         python: ["3.9", "3.13"]
     steps:
       - uses: actions/checkout@v4
+        with:
+          ref: "${{ github.event.pull_request.merge_commit_sha }}"
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
@@ -82,6 +86,8 @@ jobs:
         python: ["3.9"]
     steps:
       - uses: actions/checkout@v4
+        with:
+          ref: "${{ github.event.pull_request.merge_commit_sha }}"
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
@@ -117,6 +123,8 @@ jobs:
         python: ["3.9", "3.13"]
     steps:
       - uses: actions/checkout@v4
+        with:
+          ref: "${{ github.event.pull_request.merge_commit_sha }}"
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
@@ -152,6 +160,8 @@ jobs:
         python: ["3.9", "3.13"]
     steps:
       - uses: actions/checkout@v4
+        with:
+          ref: "${{ github.event.pull_request.merge_commit_sha }}"
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
@@ -192,6 +202,7 @@ jobs:
         uses: actions/checkout@v4
         with:
           fetch-depth: 0
+          ref: "${{ github.event.pull_request.merge_commit_sha }}"
       - name: Set up Python
         uses: actions/setup-python@v5
         with: