fix: share CLI flags between main parser and optimize subparser

[mashraf-222]

Problem

30 CLI flags (--verbose, --no-pr, --file, --function, --all, --trace-only, etc.) were defined only on the main ArgumentParser. When using the optimize subparser path (codeflash optimize mvn test ...), these flags were silently dropped by argparse — the subparser didn't recognize them and they were treated as part of the Java command.

This broke virtually every flag for the optimize subparser path, which is the primary entry point for Java optimization.

Root Cause

_build_parser() in cli.py added all 30+ flags to the main parser only. The optimize subparser was created with subparsers.add_parser("optimize") but didn't inherit any of these flags.

Fix

Used argparse's parents=[] pattern:

1. Created shared_flags = ArgumentParser(add_help=False) containing all shared flags
2. Both the main parser and optimize subparser use parents=[shared_flags]
3. Added --trace-only flag (was missing entirely)
4. Aligned max_function_count default to 256 (was 100 on subparser vs 256 elsewhere)

Test Coverage

• 10 new unit tests in tests/test_cli_args.py:
  • 7 tests verify flags work on the optimize subparser (--verbose, --no-pr, --file, --function, multiple flags, command isolation, max_function_count default)
  • 3 tests verify flags still work on the main parser path (no regression)

Testing

$ uv run pytest tests/test_cli_args.py -v
10 passed