use command arg for pr-sha

.github/workflows/slash_command_dispatch.yml

@@ -13,13 +13,14 @@ jobs:
         with:
           result-encoding: string
           script: |
-            const { owner, repo, number } = context.issue;
-            const pr = await github.rest.pulls.get({
-              owner,
-              repo,
-              pull_number: number,
-            });
-            return pr.data.head.sha
+            const body = context.payload.comment.body.trim();
+            const commandRegex = /^\/platform_tests\s+([a-f0-9]{40})$/;
+            const match = body.match(commandRegex);
+            if (!match) {
+              throw new Error("Invalid command format. Please provide a full 40-character SHA as an argument.");
+            }
+            console.log(`Extracted SHA: "${match[1]}"`);
+            return match[1];
       - name: Get PR number
         id: pr_number
         uses: actions/github-script@v7