Fix ambiguous-width character handling for CJK terminals

[sandip13579]

Summary

get_character_cell_size() currently returns a width of 1 for East Asian Width (EAW) ambiguous characters.

Many CJK terminals render these characters using two cells, which can lead to incorrect text alignment.

This PR updates the fallback logic to return 2 for characters whose East Asian Width category is "A".

Testing

• Verified that get_character_cell_size("…") previously returned 1.
• Verified that it now returns 2.
• Added/updated tests for the new behavior.

[sandip13579]

I implemented a local fix that returns a width of 2 for East Asian Width (EAW="A") characters, and it resolves the alignment issue on CJK terminals. However, I realized this changes the default behavior for all users, which could cause incorrect alignment on terminals that follow the Unicode default of treating ambiguous-width characters as width 1.

It seems that a configurable or terminal-aware approach might be a better long-term solution. I'd appreciate guidance on the preferred direction before spending more time implementing it.