Function lowercase_leading_word 

pub fn lowercase_leading_word(text: &str) -> String

Lowercase a leading capitalized plain word so text reads as a clause continuing a sentence (for example after a colon). Acronyms and identifiers (a second uppercase letter, a digit, or punctuation after the first letter) and the pronoun “I” keep their case.

assert_eq!(lowercase_leading_word("Tool calls were rejected"), "tool calls were rejected");
assert_eq!(lowercase_leading_word("MCP server failed"), "MCP server failed");
assert_eq!(lowercase_leading_word("I cannot help"), "I cannot help");
assert_eq!(lowercase_leading_word("A"), "a");