Optimize the style of error message

[pearmini]

@jackbdu Optimize the error message. This PR only optimizes its visual output, making it more obvious!

Now the prefix is different between normal output and error output. It can help users to quickly tell the difference, which is also easier to implement.

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Pull Request Overview

This PR optimizes error message display by introducing visual differentiation between normal output and error output using distinct prefixes and styling.

• Introduces a new error mark symbol (✗) to distinguish errors from regular output (➜)
• Updates the formatting system to use different prefixes for errors vs normal output
• Adds CSS styling to visually highlight error lines with red coloring and background patterns

Reviewed Changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
runtime/constant.js	Adds ERROR_MARK constant for the new error symbol
runtime/index.js	Implements separate formatting functions for errors vs output and updates error handling
editor/outputLines.js	Updates line detection to handle both output and error marks with type classification
editor/decoration.js	Adds error-specific line decoration styling
editor/index.css	Defines CSS styles for error lines with red background pattern and text color
test/output/syntaxError2.js	Updates test expectation to use new error prefix
test/output/syntaxError.js	Updates test expectation with new error prefix and additional context
test/output/runtimeError.js	Updates test expectation showing both error and success output with different prefixes
test/js/syntax-error.js	Expands test case with more comprehensive code example
test/js/runtime-error.js	Expands test case to include both error and success scenarios

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