fix: prevent double-trigger of Claude Code on same issue

Remove issue opening trigger from claude.yml to avoid conflicts with
spec-to-code.yml workflow. Now Claude Code only triggers on comments,
enabling clean approved workflow:

1. Create issue without @claude
2. Add 'approved' label
3. spec-to-code.yml posts @claude comment
4. claude.yml triggers on comment (not on issue opening)

This prevents the issue where Claude Code would trigger twice for the
same issue and ignore the second trigger.

Author: claude

.github/workflows/claude.yml

@@ -5,8 +5,6 @@ on:
     types: [created]
   pull_request_review_comment:
     types: [created]
-  issues:
-    types: [opened, assigned]
   pull_request_review:
     types: [submitted]
 
@@ -15,8 +13,7 @@ jobs:
     if: |
       (github.event_name == 'issue_comment' && contains(github.event.comment.body, '@claude')) ||
       (github.event_name == 'pull_request_review_comment' && contains(github.event.comment.body, '@claude')) ||
-      (github.event_name == 'pull_request_review' && contains(github.event.review.body, '@claude')) ||
-      (github.event_name == 'issues' && (contains(github.event.issue.body, '@claude') || contains(github.event.issue.title, '@claude')))
+      (github.event_name == 'pull_request_review' && contains(github.event.review.body, '@claude'))
     runs-on: ubuntu-latest
     permissions:
       contents: write        # Allow commits