Highlight Whole-Word Matches and Merge Overlapping Spans

Highlight every whole-word occurrence of any supplied phrase in a text. Merge overlapping matched spans before inserting tags, so overlapping matches do not produce nested or duplicated highlight tags. Implement `highlight_matches(text, phrases)`, with `text: string`, `phrases: string[]`, and return type `string`. Surround each merged span with the literal tags `<mark>` and `</mark>`. ### Constraints & Assumptions - Matching is case-sensitive and uses exact phrase characters, including internal spaces. - For this practice contract, word characters are ASCII letters, digits, and underscore. A phrase matches only when the character immediately before it, if any, and the character immediately after it, if any, are not word characters. - Every phrase is nonempty and begins and ends with a word character. The text and phrases contain no `<` or `>` characters, so inserted tags cannot be confused with source text. - `blue` does not match the prefix of `blueprint`. It does match in `blue sky` and `blue!`. - Use half-open character intervals. Merge spans only when they overlap; exactly adjacent spans remain separate. - Duplicate phrases or duplicate matches do not create additional tags. - There are at most 10,000 text characters and 100 phrases, each at most 100 characters long. All characters are ASCII. - These explicit boundary, case, tag, and adjacency rules resolve details not fixed in the report. ### Examples ```text text = "blue sky and blueprint" phrases = ["blue", "blue sky"] result = "<mark>blue sky</mark> and blueprint" ``` ```text text = "red blue green" phrases = ["red blue", "blue green"] result = "<mark>red blue green</mark>" ``` ```hint Keep positions in the original text First collect and combine original-text spans. Inserting tags while still searching changes later character positions. ```