t27 basics 25: four mistakes and what t27c says

Four small mistakes in a t27 spec and the exact message the real compiler printed for each. Lesson 25 of the t27 basics course.

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Where the numbers come from

The lesson spec public/t27/files/specs/basics/25_reading_errors.t27, compiled clean on 7 backends by public/t27/t27_compiler.wasm, whose tests pass in the site test runner
Compiler verdicts, error lines, code and counts quoted on this page are what the same wasm answered in node 22 when the course was authored; words without a run behind them are said to be read, not run