You are given a string `text` and a list of strings `sources`. For every exact occurrence of any string in `sources` within `text`, wrap the matched characters with `<yellow>` and `</yellow>`. Rules: - Matching must be exact substring matching. - Matching is case-sensitive. - If multiple matched ranges overlap or are adjacent, merge them into one highlighted region and use only one pair of tags for the merged region. - Return the final tagged string. Example: - `text = "abcxyz123"` - `sources = ["abc", "xyz", "z12"]` - Matched ranges are `[0,3)`, `[3,6)`, and `[5,8)` - After merging, the highlighted range is `[0,8)` - Output: `"<yellow>abcxyz12</yellow>3"` Follow-up: 1. Count how many exact occurrences each source string has in the original `text`. 2. For each merged highlighted region, return the list of source strings that contributed at least one match inside that region.