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

[ForgedFinancial]

Summary

• Preserves Ctrl+J as a multiline newline shortcut on macOS instead of binding it to prompt submit
• Updates the startup/tips copy to surface Ctrl+J first, while keeping Alt+Enter as a forwarded-terminal option
• Adds focused regression coverage for macOS keybinding behavior and the multiline tip

Test plan

• .venv/bin/python -m pytest -o addopts="-m 'not integration'" -q tests/cli/test_ctrl_enter_newline.py tests/cli/test_cli_init.py tests/hermes_cli/test_tips.py
• direct keybinding assertion: macos_ctrl_j_preserve_and_keybinding_assertion=PASS
• git diff --check

[alt-glitch]

Duplicate of #25111 (same author, same approach, 3rd resubmission). The most comprehensive open fix for the Ctrl-J/c-j macOS keybinding issue is #22911, which also handles Warp terminal. Root issue: #22908.

[teknium1]

Thanks for the focused fix. I verified the underlying bug still exists on current main: _preserve_ctrl_enter_newline() has no native macOS branch at cli.py:2716-2751, so _bind_prompt_submit_keys() still binds c-j to submit at cli.py:2768-2770, and the newline handler only registers when that predicate is true at cli.py:11308-11322.

Problems

• The handle_ctrl_enter_newline docstring is still Windows/WSL/SSH/Windows Terminal-specific at cli.py:11311-11320; after adding macOS, that inline documentation would be stale.
• The PR diff for cli.py around _preserve_ctrl_enter_newline() includes user-specific wording (On Danny's MacBook). That should be generalized to the platform/terminal behavior and root issue [Bug]: Shift+Enter no longer inserts a newline in classic Hermes CLI #22908.

Suggested changes

• Preserve the current main Ghostty detection branches at cli.py:2735-2740 while adding the macOS behavior, since those were merged after this PR was opened.
• Update the newline-handler docstring at cli.py:11311-11320 to mention native macOS once darwin is included.
• Replace the user-specific comment with neutral wording such as native macOS terminals that deliver the multiline shortcut as bare LF/c-j.

This is an automated hermes-sweeper review.

[teknium1]

Thanks for the focused classic-CLI regression coverage. The macOS premise still holds on current main: local macOS falls through _preserve_ctrl_enter_newline() at cli.py:3149-3171, so _bind_prompt_submit_keys() binds c-j to submit at cli.py:3189-3190, while the newline handler is conditional at cli.py:13583-13597.

Problems

• Current main added Ghostty preservation at cli.py:3155-3159 in cf8862cfa; this PR branch predates those checks. Preserve them while adding darwin, or Ghostty/tmux newline behavior would regress.
• Adding macOS also requires updating the Windows-only descriptions at cli.py:3181-3186 and cli.py:13586-13595.
• The PR-head predicate docstring at cli.py:2141-2142 refers to “Danny's MacBook”; use neutral platform/terminal wording instead.

Suggested changes

• Salvage the darwin branch into the current predicate without dropping the Ghostty branches from cf8862cfa.
• Update both current inline keybinding docstrings to name native macOS.
• Generalize the user-specific wording.

This is an automated hermes-sweeper review.

[teknium1]

When salvaging this onto current main, retain the later Ghostty checks added by cf8862cfa (current cli.py:3155-3159). This branch predates them, and replacing the predicate wholesale would make Ghostty/tmux c-j submit again.

[teknium1]

Please replace the user-specific “Danny's MacBook” explanation with neutral wording about native macOS terminals and bare LF/c-j delivery.