Fix workflow failure by adding workflow_dispatch trigger

The backfill-duplicate-comments script was failing because it tried to trigger
claude-dedupe-issues.yml via workflow_dispatch, but that workflow only had an
issues trigger. Added workflow_dispatch with issue_number input and updated the
prompt to use either event or input issue number.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

.github/workflows/backfill-duplicate-comments.yml

@@ -0,0 +1,44 @@
+name: Backfill Duplicate Comments
+description: Triggers duplicate detection for old issues that don't have duplicate comments
+
+on:
+  workflow_dispatch:
+    inputs:
+      days_back:
+        description: 'How many days back to look for old issues'
+        required: false
+        default: '90'
+        type: string
+      dry_run:
+        description: 'Dry run mode (true to only log what would be done)'
+        required: false
+        default: 'true'
+        type: choice
+        options:
+          - 'true'
+          - 'false'
+
+jobs:
+  backfill-duplicate-comments:
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    permissions:
+      contents: read
+      issues: read
+      actions: write
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+      
+      - name: Setup Bun
+        uses: oven-sh/setup-bun@v2
+        with:
+          bun-version: latest
+      
+      - name: Backfill duplicate comments
+        run: bun run scripts/backfill-duplicate-comments.ts
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          DAYS_BACK: ${{ inputs.days_back }}
+          DRY_RUN: ${{ inputs.dry_run }}

.github/workflows/claude-dedupe-issues.yml

@@ -3,6 +3,12 @@ description: Automatically dedupe GitHub issues using Claude Code
 on:
   issues:
     types: [opened]
+  workflow_dispatch:
+    inputs:
+      issue_number:
+        description: 'Issue number to process for duplicate detection'
+        required: true
+        type: string
 
 jobs:
   claude-dedupe-issues:
@@ -19,7 +25,7 @@ jobs:
       - name: Run Claude Code slash command
         uses: anthropics/claude-code-base-action@beta
         with:
-          prompt: "/dedupe ${{ github.repository }}/issues/${{ github.event.issue.number }}"
+          prompt: "/dedupe ${{ github.repository }}/issues/${{ github.event.issue.number || inputs.issue_number }}"
           anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
           claude_env: |
             GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}