Rename `block` parsing rule to `fn` by adding TOKEN_FN token and function prefix rule, removing the old block prefix from TOKEN_LEFT_BRACE. Update compiler.c to replace `block()` with `function()` and add fn equality primitives (fn_eqeq, fn_bangeq) in primitives.c. Migrate test files: rename block_call.wren to fn_call.wren, block_syntax.wren to fn_syntax.wren, and replace `{ ... }` with `fn { ... }` or `fn expr` syntax. Remove obsolete bool_equality.wren test.
Add support for testing compile errors by introducing `// expect error` annotations in test files. The test runner now validates that expected errors occur on specific lines and that the compiler exits with code 1 when errors are present. The compiler's error output is enhanced to include line numbers in the format `[Line N] Error`, and the `Token` struct gains a `line` field to track token positions. The main entry point returns exit code 1 when compilation fails, enabling the test runner to verify error exit codes.
