Release ZCompare v0.1.2 detail highlighting fixes

[Zcube7]

Summary

• Add character-level highlighting for changed cell text in both worksheet grids and the full-value dialog.
• Make long raw/display values accessible without truncating copied content.
• Fix the WPF Run double-click crash and keep real brackets, spaces, tabs, newlines, and trailing whitespace unchanged when copying.
• Bump the product, installer, CLI, reports, and documentation to v0.1.2.

用户可见更新

• 工作表和完整值详情中用深红色精确突出变化字符。
• 长单元格内容可横向查看，复制内容保持原始字符和空白不变。
• 修复双击差异文字时程序异常退出的问题。
• 移除详情中人工添加的 ⟦ ⟧ 差异标记。

Validation

• Release build with warnings as errors: 0 warnings, 0 errors.
• Core/CLI tests: 156 passed.
• App tests: 70 passed.
• Public content and reachable Git history scan: passed.
• Local portable package validation: passed (2.60 MiB, no PDB/test/private-data files).
• The installer will be built and validated by the protected Windows release workflow, which installs Inno Setup 6 in CI.