fix(cli): preserve Ctrl-J newline on macOS

[ForgedFinancial]

Summary

• preserve c-j/Ctrl-J as a multiline newline shortcut on macOS instead of binding it to submit
• keep bare local Linux c-j submit fallback unchanged
• update CLI help text and focused tests

Verification

• python -m pytest -q -n 0 tests/cli/test_ctrl_enter_newline.py tests/cli/test_cli_init.py::TestPromptToolkitTerminalCompatibility::test_lf_enter_binds_to_submit_handler_posix

[alt-glitch]

Related to / competes with #22911 (same fix: preserve c-j for newline on macOS). Also competes with #22495 (Ctrl+Enter newline over SSH/WSL). These should be coordinated to avoid conflicts.

[ForgedFinancial]

MacBook verification refresh: the same Ctrl+J macOS newline fix was re-applied and tested on current Danny MacBook Hermes source. Evidence: local main 948084734 contains the patch; refreshed remote safety branch ForgedFinancial:fix/macos-ctrl-j-newline-durable-2026-05-12 points to 948084734; focused tests passed: 11 passed in tests/cli/test_ctrl_enter_newline.py plus test_cli_init LF submit compatibility; macOS _preserve_ctrl_enter_newline assertion passed; canonical bootstrap now enforces HERMES_CTRL_J_NEWLINE_CHECK=PASS in ForgedFinancial/canonical-workspace#35. Merge attempt from ForgedFinancial failed due upstream permission: MergePullRequest not permitted, so PR remains open/mergeable for maintainers.