ci(docs-claude-review): Update comments instead of creating new ones (#12106)

## Changes 🏗️

This PR updates the Claude Block Docs Review CI workflow to update
existing comments instead of creating new ones on each push.

### What's Changed:
1. **Concurrency group** - Prevents race conditions if the workflow runs
twice simultaneously
2. **Comment cleanup step** - Deletes any previous Claude review comment
before posting a new one
3. **Marker instruction** - Instructs Claude to include a `<!--
CLAUDE_DOCS_REVIEW -->` marker in its comment for identification

### Why:
Previously, every PR push would create a new review comment, cluttering
the PR with multiple comments. Now only the most recent review is shown.

### Testing:
1. Create a PR that triggers this workflow (modify a file in
`docs/integrations/` or `autogpt_platform/backend/backend/blocks/`)
2. Verify first run creates comment with marker
3. Push another commit
4. Verify old comment is deleted and new comment is created (not
accumulated)

Requested by @Bentlybro

---

## Checklist 📋

#### For code changes:
- [x] I have clearly listed my changes in the PR description
- [ ] I have made a test plan
- [ ] I have tested my changes according to the test plan (will be
tested on merge)

#### For configuration changes:
- [x] `.env.default` is updated or already compatible with my changes
- [x] `docker-compose.yml` is updated or already compatible with my
changes
- [x] I have included a list of my configuration changes in the PR
description (under **Changes**)

<!-- greptile_comment -->

<h2>Greptile Overview</h2>

<details><summary><h3>Greptile Summary</h3></summary>

Added concurrency control and comment deduplication to prevent multiple
Claude review comments from accumulating on PRs. The workflow now
deletes previous review comments (identified by `<!-- CLAUDE_DOCS_REVIEW
-->` marker) before posting new ones, and uses concurrency groups to
prevent race conditions.
</details>


<details><summary><h3>Confidence Score: 5/5</h3></summary>

- This PR is safe to merge with minimal risk
- The changes are well-contained, follow GitHub Actions best practices,
and use built-in GitHub APIs safely. The concurrency control prevents
race conditions, and the comment cleanup logic uses proper filtering
with `head -1` to handle edge cases. The HTML comment marker approach is
standard and reliable.
- No files require special attention
</details>


<details><summary><h3>Sequence Diagram</h3></summary>

```mermaid
sequenceDiagram
    participant GH as GitHub PR Event
    participant WF as Workflow
    participant API as GitHub API
    participant Claude as Claude Action
    
    GH->>WF: PR opened/synchronized
    WF->>WF: Check concurrency group
    Note over WF: Cancel any in-progress runs<br/>for same PR number
    WF->>API: Query PR comments
    API-->>WF: Return all comments
    WF->>WF: Filter for CLAUDE_DOCS_REVIEW marker
    alt Previous comment exists
        WF->>API: DELETE comment by ID
        API-->>WF: Comment deleted
    else No previous comment
        WF->>WF: Skip deletion
    end
    WF->>Claude: Run code review
    Claude->>API: POST new comment with marker
    API-->>Claude: Comment created
```
</details>


<sub>Last reviewed commit: fb1b436</sub>

<!-- greptile_other_comments_section -->

<!-- /greptile_comment -->

.github/workflows/docs-claude-review.yml

@@ -7,6 +7,10 @@ on:
       - "docs/integrations/**"
       - "autogpt_platform/backend/backend/blocks/**"
 
+concurrency:
+  group: claude-docs-review-${{ github.event.pull_request.number }}
+  cancel-in-progress: true
+
 jobs:
   claude-review:
     # Only run for PRs from members/collaborators
@@ -91,5 +95,35 @@ jobs:
             3. Read corresponding documentation files to verify accuracy
             4. Provide your feedback as a PR comment
 
+            ## IMPORTANT: Comment Marker
+            Start your PR comment with exactly this HTML comment marker on its own line:
+            <!-- CLAUDE_DOCS_REVIEW -->
+
+            This marker is used to identify and replace your comment on subsequent runs.
+
             Be constructive and specific. If everything looks good, say so!
             If there are issues, explain what's wrong and suggest how to fix it.
+
+      - name: Delete old Claude review comments
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          # Get all comment IDs with our marker, sorted by creation date (oldest first)
+          COMMENT_IDS=$(gh api \
+            repos/${{ github.repository }}/issues/${{ github.event.pull_request.number }}/comments \
+            --jq '[.[] | select(.body | contains("<!-- CLAUDE_DOCS_REVIEW -->"))] | sort_by(.created_at) | .[].id')
+
+          # Count comments
+          COMMENT_COUNT=$(echo "$COMMENT_IDS" | grep -c . || true)
+
+          if [ "$COMMENT_COUNT" -gt 1 ]; then
+            # Delete all but the last (newest) comment
+            echo "$COMMENT_IDS" | head -n -1 | while read -r COMMENT_ID; do
+              if [ -n "$COMMENT_ID" ]; then
+                echo "Deleting old review comment: $COMMENT_ID"
+                gh api -X DELETE repos/${{ github.repository }}/issues/comments/$COMMENT_ID
+              fi
+            done
+          else
+            echo "No old review comments to clean up"
+          fi