fix: use artifact-based PR number passing for draft conversion

The API-based PR lookup from workflow_run context does not work for
pull_request_review triggers as head_branch refers to the default
branch, not the PR branch. Switch back to accepting pr_number as
an input, with integer validation.

Author: chrisburr

.github/workflows/draft-on-changes-requested.yml

@@ -2,6 +2,10 @@ name: Draft on Changes Requested
 
 on:
   workflow_call:
+    inputs:
+      pr_number:
+        required: true
+        type: number
     secrets:
       token:
         required: true
@@ -15,29 +19,20 @@ jobs:
         with:
           github-token: ${{ secrets.token }}
           script: |
-            const run = context.payload.workflow_run;
-            if (!run) {
-              core.setFailed("This workflow must be called from a workflow_run trigger.");
+            const prNumber = ${{ inputs.pr_number }};
+            if (!Number.isInteger(prNumber) || prNumber <= 0) {
+              core.setFailed(`Invalid PR number: ${prNumber}`);
               return;
             }
 
-            const owner = run.head_repository.owner.login;
-            const branch = run.head_branch;
-            const { data: prs } = await github.rest.pulls.list({
+            const { data: pr } = await github.rest.pulls.get({
               owner: context.repo.owner,
               repo: context.repo.repo,
-              state: "open",
-              head: `${owner}:${branch}`,
+              pull_number: prNumber,
             });
 
-            if (prs.length === 0) {
-              core.info("No open PR found for this branch.");
-              return;
-            }
-
-            const pr = prs[0];
             if (pr.draft) {
-              core.info(`PR #${pr.number} is already a draft, skipping.`);
+              core.info(`PR #${prNumber} is already a draft, skipping.`);
               return;
             }
 
@@ -49,4 +44,4 @@ jobs:
               }
             `, { id: pr.node_id });
 
-            core.info(`Converted PR #${pr.number} to draft.`);
+            core.info(`Converted PR #${prNumber} to draft.`);