fix(flags): preserve parsed flags when --help is combined with -D

[seanseannery]

Key Changes

• ParseOpsFlags now returns populated OpsFlags alongside ErrHelp instead of a zero-value struct, so flags like -D parsed before --help/-h/-? are preserved
• The -? handler now strips -? from args and still runs fs.Parse on the remaining flags before returning ErrHelp
• 3 new test cases verify -D is preserved when combined with each help variant (--help, -h, -?)
• Test harness updated to assert on wantFlags even in error cases

Why do we need this?

When -D /path --help was passed, the --help path in main.go used flags.Directory to locate the Opsfile for the command listing. But ParseOpsFlags was returning OpsFlags{} (zero value) on all help paths, so flags.Directory was always empty and the Opsfile was never found. This broke the --help + -D integration added in #36.

Related to #19

New modules or other dependencies introduced

None

How was this tested?

• 3 new unit tests: -D combined with --help, -D combined with -h, -D combined with -? — all verify OpsFlags.Directory is populated alongside ErrHelp
• Manual smoke test: ops -D ./examples --help now shows the command listing
• make lint and make test pass