Implement run-length encoding to compress a string by replacing consecutive characters with the character followed by its count. If the compressed string is not shorter than the original, return the original string.

This technique is useful for reducing storage in custom objects, optimizing API payloads, or implementing custom data compression in Salesforce.

Examples:

Input: input = "aaa" Output: "a3" Explanation: Three consecutive 'a' characters compress to 'a3' Input: input = "abc" Output: "abc" Explanation: No consecutive characters, so compression does not help Input: input = "aaabbc" Output: "a3b2c1" Explanation: 'aaa' becomes 'a3', 'bb' becomes 'b2', 'c' becomes 'c1' Input: input = "" Output: "" Explanation: Empty string returns empty string
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