Find First Anagram Occurrence

Given two strings `text` and `pattern`, return the starting index of the first substring in `text` that is an anagram of `pattern`. If no such substring exists, return `-1`. A substring is an anagram of `pattern` if it has exactly the same character frequencies as `pattern`, possibly in a different order. Assume the input strings contain lowercase English letters unless otherwise specified. Example: ```text text = "cbaebabacd" pattern = "abc" ``` The substrings of length `3` are checked from left to right. The first substring that is an anagram of `"abc"` is `"cba"`, so the answer is `0`. Follow-up: Explain how your approach would scale if `text` were extremely large, streamed in chunks, or distributed across multiple machines.