fix(codeagent-wrapper): remove binary artifacts and improve error messages

- Remove committed binaries from git tracking (codeagent-wrapper, *.test)
- Remove coverage.out from tracking (generated by CI)
- Update .gitignore to exclude build artifacts
- Add task block index to parallel config error messages for better debugging

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

codeagent-wrapper/.gitignore

@@ -1,3 +1,9 @@
+# Build artifacts
+codeagent-wrapper
+codeagent-wrapper.exe
+*.test
+
+# Coverage reports
 coverage.out
 coverage*.out
 cover.out