Fix TitleCase capitalization at sentence boundaries

[mohammedbakri123]

Fixes #1658

Problem

ToTitleCase does not capitalize the first word of a sentence when that word is an article, conjunction, or preposition.

Solution

Capitalize words at sentence boundaries (start of string or after ., !, ?) while preserving existing TitleCase rules for other positions.

Tests

• dotnet test --project Humanizer.Tests --framework net10.0

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 5568efc216

ℹ️ About Codex in GitHub

Codex has been enabled to automatically review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

When you sign up for Codex through ChatGPT, Codex can also answer questions or update the PR, like "@codex address that feedback".

[chatgpt-codex-connector]

Treat words after closing quotes/parens as sentence starts

The new sentence-start detection only looks at the first non-whitespace character before the word, so if a sentence ends with punctuation followed by a closing quote or parenthesis (e.g., "Hello." the or "Hello." (the ...)) the previous non-whitespace character becomes "/), not ., !, or ?. In those cases IsSentenceStart returns false and articles/conjunctions/prepositions right after a real sentence boundary remain lowercase, which regresses the intended behavior for quoted or parenthesized sentences.

Useful? React with 👍 / 👎.