Build from the base branch, not just target it

CodeRabbit caught this on the multisite PR and it applies identically here:
`base` only set the PR target, while actions/checkout took no ref at all. Since
create-pull-request commits onto whatever HEAD it finds, dispatching from
feature/foo with base develop would build feature/foo and then raise a PR into
develop containing every commit between the two - not just the POT change.

Checkout now uses the same `base` expression, so one value decides what gets
built, what the PR branch is named, and what it targets. There is no
combination of inputs that makes them disagree.

The develop default is dropped from the input at the same time: with base now
driving the checkout, a hardcoded default would silently ignore the branch
picked in the dispatch UI. Empty falls back to the dispatched branch, so the
picker behaves as expected and build and target still match.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019LoLgW7oFjBPxGea9kiZJ2

Author: pattonwebz

.github/workflows/make-pot.yml

@@ -4,9 +4,8 @@ on:
   workflow_dispatch:
     inputs:
       base:
-        description: 'Base branch to compare and create PR against.'
+        description: 'Base branch to build from and create the PR against. Leave empty to use the branch this was dispatched on.'
         required: false
-        default: 'develop'
 
 # Manual dispatch only - deliberately no push or pull_request trigger, so this
 # never fires off a branch or a PR. That is also why there is no branch gating
@@ -16,8 +15,15 @@ jobs:
   make-pot:
     runs-on: ubuntu-latest
     steps:
+      # Checked out at `base`, not just PR'd against it. create-pull-request
+      # commits onto whatever HEAD it finds, so if this built one branch and
+      # targeted another, every commit between the two would be swept into the
+      # translation PR. Empty input falls back to the dispatched branch, which
+      # keeps build and target the same by default.
       - name: Checkout code
         uses: actions/checkout@v4
+        with:
+          ref: ${{ github.event.inputs.base || github.ref_name }}
 
       - name: Set up Node.js
         uses: actions/setup-node@v4
@@ -103,6 +109,6 @@ jobs:
           commit-message: Update POT translation file
           title: Update POT translation file
           body: This PR updates the POT translation file generated by the workflow.
-          branch: update-translations/${{ github.ref_name }}
+          branch: update-translations/${{ github.event.inputs.base || github.ref_name }}
           base: ${{ github.event.inputs.base || github.ref_name }}
           delete-branch: true