chore: remove test files from repository

Removed 10 test_*.arc files that were used during development:
- test_connections.arc
- test_current_syntax.arc
- test_minimal.arc
- test_new_syntax.arc
- test_simple.arc
- test_syntax_1_full.arc
- test_syntax_2_full.arc
- test_syntax_3_full.arc
- test_system_syntax.arc
- test_third_syntax.arc

These files should not be version-controlled as they are temporary development artifacts.

Author: Mbaroudi