feat: unified PR report combining bundle size and runtime perf (#9911)

## Summary

Replaces two separate PR comment workflows (bundle size + performance)
with a single unified report that posts one combined comment per PR.

## Changes

- **What**: New `pr-report.yaml` aggregator workflow triggers on both
`CI: Size Data` and `CI: Performance Report` completions. Finds sibling
workflow runs by PR head SHA. Renders combined report via
`unified-report.js` (shells out to existing `size-report.js` and
`perf-report.ts`). Sections show "pending" or "failed" placeholders when
data is unavailable.
- **Breaking**: Removes `pr-size-report.yaml` and `pr-perf-report.yaml`.
Legacy `<!-- COMFYUI_FRONTEND_SIZE -->` and `<!-- COMFYUI_FRONTEND_PERF
-->` comments are auto-cleaned on first run.
- **Dependencies**: None

## Review Focus

- Concurrency key uses `head_sha` so the later-completing workflow
cancels the earlier report run, ensuring the final comment always has
both sections.
- Stale-run guard: verifies workflow_run SHA matches the live PR head
before posting.
- The `workflow_dispatch` re-trigger path from `pr-size-report.yaml` is
not carried forward — the unified workflow handles re-trigger naturally
via its dual-trigger design.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-9911-feat-unified-PR-report-combining-bundle-size-and-runtime-perf-3236d73d365081baac1cce6f0d9244ac)
by [Unito](https://www.unito.io)

---------

Co-authored-by: GitHub Action <action@github.com>

.github/workflows/ci-size-data.yaml

@@ -8,6 +8,10 @@ on:
     branches:
       - main
 
+concurrency:
+  group: size-${{ github.ref }}
+  cancel-in-progress: true
+
 permissions:
   contents: read
 
@@ -28,11 +32,12 @@ jobs:
       - name: Collect size data
         run: node scripts/size-collect.js
 
-      - name: Save PR number & base branch
+      - name: Save PR metadata
         if: ${{ github.event_name == 'pull_request' }}
         run: |
           echo ${{ github.event.number }} > ./temp/size/number.txt
           echo ${{ github.base_ref }} > ./temp/size/base.txt
+          echo ${{ github.event.pull_request.head.sha }} > ./temp/size/head-sha.txt
 
       - name: Upload size data
         uses: actions/upload-artifact@v6