Remove --legacy-console CLI option and add regression test

[sodejm]

Motivation

• Remove the special-cased --legacy-console startup path so CLI arguments are handled consistently by the normal parser path.
• Preserve existing behaviors for no-argument REPL startup, one-shot command dispatch, and the modules list --json contract while removing the legacy entrypoint.

Description

• Deleted the special conditional branch in main() that intercepted arguments == ["--legacy-console"] so non-empty argument lists are always parsed via build_parser().
• Kept the no-argument REPL behavior which still calls run_repl() when arguments is empty.
• Updated tests/modular/test_repl_shell.py to remove the legacy-console expectation and added test_main_rejects_legacy_console_like_unknown_or_unsupported_options which asserts `[

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[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Update docs before dropping legacy console flag

Now that non-empty arguments always fall through to the normal parser path here, ancestry --legacy-console exits with a usage error, but the shipped docs still advertise that exact command as the temporary cmd2 compatibility fallback in docs/CONSOLE.md:10-18 and docs/REPL_ARCHITECTURE.md:18-19,87-108. Users following those docs will lose the documented fallback, so the removal should update or delete those compatibility-path sections in the same change.

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