feat: add PR assignment check workflow

Author: maxprilutskiy

.github/workflows/pr-assignment-check.yml

@@ -0,0 +1,38 @@
+name: PR Assignment Check
+
+on:
+  pull_request_target:
+    types: [opened, reopened, edited]
+  workflow_dispatch:
+    inputs:
+      pr_number:
+        description: 'PR number to check'
+        required: true
+        type: number
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      issues: read
+      pull-requests: write
+    steps:
+      - uses: anthropics/claude-code-action@v1
+        with:
+          anthropic_api_key: ${{ secrets.CLAUDE_CODE_ANTHROPIC_API_KEY }}
+          prompt: |
+            EXEMPT USERS: @maxprilutskiy, @vrcprl, @davidturnbull, @monicabe, @sumitsaurabh927, @AleksandrSl (skip all checks if PR author is one of these)
+
+            Check if this PR references any issues (via "Closes #123", "Fixes #456", etc.).
+
+            For each referenced issue:
+            1. Check if the issue has assignees
+            2. If yes, check if the PR author is one of the assignees
+            3. If the PR author is NOT an assignee, close this PR with a brief, friendly comment (2-3 sentences, no emojis) explaining:
+               - The issue was already assigned to someone else
+               - They should wait to be assigned before submitting PRs
+               - Encourage them to find other unassigned issues
+
+            If no issues referenced or PR author is properly assigned, do nothing.
+          claude_args: "--max-turns 3"