Fixes: #63864

This restores REPL dot-command handling when a command is entered from a TTY multiline continuation prompt.

Since TTY multiline input can arrive as one editable buffer like function a() {\n.break, the previous command detection only checked the beginning of the full buffer and sent .break, .help, and .exit to JavaScript evaluation, producing Uncaught SyntaxError: Unexpected token '.'.

This change checks the newest physical line for registered REPL dot-commands in the TTY multiline case, keeps the preceding lines in the existing buffered-command path, and dispatches the dot-command through the existing REPL keyword handling.

Added regression coverage for:

• .break after a recoverable multiline input
• .help after a recoverable multiline input
• .exit after a recoverable multiline input

Validation:

• node --check lib/repl.js
• node --check test/parallel/test-repl-multiline.js
• git diff --check

Note: I could not run python tools/test.py test/parallel/test-repl-multiline.js locally because this Windows checkout does not currently have a built Node binary.