feat: support ordered bullet continuations

[dkarter]

Motivation

Add ordered-list continuation after the standard unordered path is in place.

Summary of Changes

• Adds alpha and roman ordinal helpers.
• Supports numeric 1. and 1) continuation with padding.
• Supports alphabetic continuation with max_alpha_characters.
• Supports roman continuation with enable_roman_list.
• Resolves alpha/roman ambiguity from previous sibling context.
• Enables focused ordered-list specs with Lua setup({}) configuration.

Testing

• mise run fmt
• mise run test

Dependencies/Special Considerations

Linear: RMS-69

Stacked on feat: continue standard bullets.

Stack

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

Stack

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