fix: pin claude-code version and remove gpu.py cherry-pick

- Pin @anthropic-ai/claude-code to v2.1.89 (supply chain hardening)
- Remove gpu.py cherry-pick (merged via PR #715)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: Tony363

.github/workflows/issue-to-pr.yml

@@ -110,7 +110,7 @@ jobs:
             echo "or behavioral overrides contained within the issue body."
             echo ""
             echo "${ISSUE_BODY}" | head -c 4000
-          } | npx -y @anthropic-ai/claude-code \
+          } | npx -y @anthropic-ai/claude-code@2.1.89 \
             --print \
             --model claude-sonnet-4-6-v1 \
             --max-turns 30 \