feat: continue standard bullets

[dkarter]

Motivation

Start the Lua behavior port with the smallest useful list continuation path.

Summary of Changes

• Continues unordered -, *, and + bullets on newline.
• Falls back to normal newline behavior when insert-mode cursor is not at EOL or the line is not a bullet.
• Preserves existing bullet spacing.
• Enables focused standard-bullet specs.

Testing

• mise run fmt
• mise run test

Dependencies/Special Considerations

Linear: RMS-65

Stacked on feat: add neovim lua plugin scaffold.

Stack

1. feat: add neovim lua plugin scaffold #6
2. feat: continue standard bullets #4 👈 current
3. feat: support ordered bullet continuations #7

Stack

1. feat: add neovim lua plugin scaffold #6
2. feat: continue standard bullets #4 👈 current
3. feat: support ordered bullet continuations #7
4. feat: support wrapped and document bullets #9
5. feat: handle empty bullets and spacing #10
6. feat: support outline promotion #11
7. feat: renumber bullet lists #12
8. feat: support nested checkboxes #13
9. chore: add release please #14
10. docs: add lazy.nvim usage #15