Fix mixed-language table alignment for 2.1.1

[ShawnBaek]

Summary

• render terminal cells with one space of left and right padding
• keep the header separator while removing separators between ordinary data rows
• calculate mixed CJK, Hangul, and emoji presentation widths consistently
• add exact ASCII and Unicode output tests for English, Chinese, Korean, and mixed scripts within a single value
• update README examples to match the new command-line table layout

Why

Unicode grapheme count does not always equal terminal display width. CJK and Hangul characters occupy two terminal columns, while emoji presentation selectors can change a symbol from one column to two. The renderer also drew borders from content widths without accounting for cell padding, which could make mixed-language tables appear misaligned.

Impact

Existing print(...), TableStyle, TableSpacing, and Logger.table(...) APIs are unchanged. Only rendered table formatting and width handling change.

Version

Target release: 2.1.1. SwiftPM package versions are Git-tag based, so the merged commit should be tagged 2.1.1 to publish the version.

Validation

• 58 Swift package tests pass
• exact ASCII and Unicode border assertions pass
• EN/CN/Korean column combinations pass
• values such as 안녕 Hello, 你好 Hello, and 你好 안녕 align correctly