Switch PR evaluation to /evaluate comment trigger

Replace auto-trigger on prediction file changes with a manual
/evaluate comment command. Only repo owners, members, and
collaborators can trigger the workflow, preventing unnecessary
CI runs on every PR update.

Author: Henry-Shan

.github/workflows/pr-evaluation.yml

@@ -1,29 +1,61 @@
 name: Router Submission Evaluation
 
 on:
-  pull_request_target:
-    types: [opened, synchronize, reopened]
-    paths:
-      - "router_inference/predictions/**"
+  issue_comment:
+    types: [created]
 
 jobs:
   evaluate-router:
+    if: >-
+      github.event.issue.pull_request &&
+      startsWith(github.event.comment.body, '/evaluate') &&
+      (
+        github.event.comment.author_association == 'OWNER' ||
+        github.event.comment.author_association == 'MEMBER' ||
+        github.event.comment.author_association == 'COLLABORATOR'
+      )
     runs-on: self-hosted
     permissions:
       contents: read
       pull-requests: write
     steps:
+      - name: Acknowledge /evaluate command
+        uses: actions/github-script@v7
+        with:
+          script: |
+            await github.rest.reactions.createForIssueComment({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              comment_id: context.payload.comment.id,
+              content: 'eyes'
+            });
+
+      - name: Fetch PR details
+        id: pr
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const pr = await github.rest.pulls.get({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              pull_number: context.payload.issue.number
+            });
+            core.setOutput('head_sha', pr.data.head.sha);
+            core.setOutput('base_ref', pr.data.base.ref);
+            core.setOutput('base_sha', pr.data.base.sha);
+            core.setOutput('number', pr.data.number);
+
       - name: Checkout base repository (for evaluation scripts)
         uses: actions/checkout@v4
         with:
-          ref: ${{ github.event.pull_request.base.ref }}
+          ref: ${{ steps.pr.outputs.base_ref }}
           path: base
           fetch-depth: 0
 
       - name: Checkout PR branch (for prediction file only)
         uses: actions/checkout@v4
         with:
-          ref: ${{ github.event.pull_request.head.sha }}
+          ref: ${{ steps.pr.outputs.head_sha }}
           path: pr
           fetch-depth: 0
 
@@ -35,8 +67,8 @@ jobs:
           set -euo pipefail
           # Compare against the upstream base branch
           # This ensures each router submission is evaluated independently
-          BASE_REF="${{ github.event.pull_request.base.ref }}"
-          BASE_SHA="${{ github.event.pull_request.base.sha }}"
+          BASE_REF="${{ steps.pr.outputs.base_ref }}"
+          BASE_SHA="${{ steps.pr.outputs.base_sha }}"
 
           if [[ -z "$BASE_SHA" ]]; then
             echo "Error: Could not determine PR base SHA" >&2
@@ -158,9 +190,9 @@ jobs:
         run: |
           set -euo pipefail; trap 'cat evaluation_output.txt' EXIT
           # Uses base repo's evaluation script (safe - not from PR)
-          BASE_SHA="${{ github.event.pull_request.base.sha }}"
+          BASE_SHA="${{ steps.pr.outputs.base_sha }}"
           uv run python automation/process_pr_submission.py \
-            --pr "${{ github.event.pull_request.number }}" \
+            --pr "${{ steps.pr.outputs.number }}" \
             --router "${{ steps.detect.outputs.router }}" \
             --split "${{ steps.detect.outputs.split }}" \
             --base-ref "$BASE_SHA" > evaluation_output.txt 2>&1
@@ -213,9 +245,21 @@ jobs:
 
             // Post comment to PR
             await github.rest.issues.createComment({
-              issue_number: context.payload.pull_request.number,
+              issue_number: context.payload.issue.number,
               owner: context.repo.owner,
               repo: context.repo.repo,
               body: comment
             });
             console.log('Successfully posted evaluation results as PR comment');
+
+      - name: React with success
+        if: ${{ steps.detect.outputs.router != '' && steps.evaluate.outcome == 'success' }}
+        uses: actions/github-script@v7
+        with:
+          script: |
+            await github.rest.reactions.createForIssueComment({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              comment_id: context.payload.comment.id,
+              content: 'rocket'
+            });