Breakpoint frontend

[Raaghulk04]

Description

This PR depends on the js-slang PR [https://github.com/source-academy/js-slang/pull/1926]. The frontend build will fail until the js-slang changes are merged and published to npm, and package.json is updated to the new version."
This PR allows users to access the step with the next/previous breakpoint in the stepper

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• Code quality improvements

How to test

Checklist

• I have tested this code
• I have updated the documentation

[gemini-code-assist]

Code Review

This pull request introduces breakpoint navigation to the substitution visualizer, allowing users to jump between debugger statements via updated UI buttons and hotkeys. The implementation includes new logic to scan content markers for debugger statements and adds a renderer for them. Feedback focuses on improving maintainability by removing commented-out code, refactoring duplicated SCSS styles into reusable mixins or placeholders, and replacing hardcoded color values with SASS variables.

[martin-henz]

Please address the issues pointed out by gemini-bot.

[coveralls]

Pull Request Test Coverage Report for Build 23936888671

Details

• 2 of 16 (12.5%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.04%) to 41.679%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/commons/sideContent/content/SideContentSubstVisualizer.tsx	2	16	12.5%

Totals
Change from base Build 23890044554:	-0.04%
Covered Lines:	5802
Relevant Lines:	12907

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💛 - Coveralls

[martin-henz]

All good.