Make beg_end math delimitor default

[Golddirio]

What is the purpose of this pull request?

• Documentation update
• Bug fix
• Feature addition or enhancement
• Code maintenance
• DevOps
• Improve developer experience
• Others, please explain:

Closes #2710

Overview of changes:
The beg_end Math delimitor is made default without the need to configure in site.json for users. Hence, the following code is no longer needed if the user would like to use beg_end:

 {
  "plugins": [
    "mathDelimiters"
  ],
  "pluginsContext" : {
    "mathDelimiters" : {
      "delimiters": ["beg_end"]
    }
  },
}

Anything you'd like to highlight/discuss:
This improvement does not affect the use of other Math delimitors. If the user would like to use other delimitors other than beg_end they still need to configure in site.json as usual.

Testing instructions:

Proposed commit message: (wrap lines at 72 characters)
Make beg_end math delimitor default

---

Checklist: ☑️

• Updated the documentation for feature additions and enhancements
• Added tests for bug fixes or features
• Linked all related issues
• No unrelated changes

---

Reviewer checklist:

Indicate the SEMVER impact of the PR:

• Major (when you make incompatible API changes)
• Minor (when you add functionality in a backward compatible manner)
• Patch (when you make backward compatible bug fixes)

At the end of the review, please label the PR with the appropriate label: r.Major, r.Minor, r.Patch.

Breaking change release note preparation (if applicable):

• To be included in the release note for any feature that is made obsolete/breaking

Give a brief explanation note about:

• what was the old feature that was made obsolete
• any replacement feature (if any), and
• how the author should modify his website to migrate from the old feature to the replacement feature (if possible).

[Copilot]

Pull Request Overview

This PR makes the beg_end math delimiter available by default without requiring explicit configuration in site.json. The change simplifies the user experience by automatically enabling support for LaTeX \begin{equation}...\end{equation} syntax.

• Introduces a new default plugin that automatically applies the beg_end math delimiter
• Removes the need for users to manually configure mathDelimiters plugin for basic equation support
• Maintains backward compatibility with existing delimiter configurations

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
packages/core/src/plugins/default/markbind-plugin-begendMathDelimitor.ts	New plugin that automatically applies beg_end delimiter using markdown-it-texmath
packages/core/test/unit/plugins/default/begendMathDelimitor.test.ts	Test coverage for the new default plugin functionality

Comments suppressed due to low confidence (1)

packages/core/test/unit/plugins/default/begendMathDelimitor.test.ts:7

• The jest.resetModules() call may not effectively reset the pluginAdded flag since it's a module-level variable. Consider testing the plugin's idempotent behavior more explicitly.

    jest.resetModules();

[Copilot]

Use ES6 import syntax instead of require() to maintain consistency with the other imports in the file.

Suggested change

	const texmath = require('markdown-it-texmath');
	import * as texmath from 'markdown-it-texmath';

[Copilot]

The global pluginAdded flag could cause issues in multi-threaded environments or when the module is imported multiple times. Consider using a more robust state management approach.

Suggested change

	};
	const plugin = {
	pluginAdded: false,
	applyBegEndDelimiters() {
	if (!this.pluginAdded) {
	// Always use 'beg_end' delimiter regardless of site.json config
	md.use(texmath, {
	engine: katex,
	delimiters: ['beg_end'], // force beg_end delimiter
	});
	this.pluginAdded = true;
	}
	},
	beforeSiteGenerate() {
	this.applyBegEndDelimiters();
	},
	};
	export = plugin;

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 52.92%. Comparing base (f681976) to head (9007072).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2737      +/-   ##
==========================================
+ Coverage   52.84%   52.92%   +0.07%     
==========================================
  Files         130      131       +1     
  Lines        7162     7173      +11     
  Branches     1591     1502      -89     
==========================================
+ Hits         3785     3796      +11     
  Misses       3072     3072              
  Partials      305      305              

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[gerteck]

Thanks @Golddirio for your PR!

The goal of enabling beg_end delimiters by default makes sense, but the approach here feels heavier than necessary.

MarkBind’s markdown pipeline already initializes markdown-it with its math delimiters in a single, central location. Instead of introducing a new plugin (with its own state, lifecycle hook, and tests), it might be worth looking at where the default delimiter list is set during markdown-it setup. That’s the same place our other delimiters (dollar, brackets) are configured.

By adjusting that initialization directly, we could achieve the same effect without adding an extra plugin layer or lifecycle dependency. This would also keep delimiter logic in one place, consistent with the architecture described here.

See: MarkBind Architecture
See: supported delimiters

Edit: Additionally, consider updating the docs as well to reflect any new changes!