Upgrade to 4.0.2 converts ID underscore to dash

Problem/Motivation

In block_class 4.0.2 on Drupal 11, when a custom HTML ID is set on a block using the "Customize the unique HTML ID of this block" field, any underscores in the ID value are automatically converted to dashes on page render.

For example, a custom block ID entered as more_to_explore is rendered in the page source as more-to-explore.

This breaks CSS selectors, JavaScript targeting, and anchor links that depend on the original underscore-based ID. The issue does not exist in block_class 2.0.11 on Drupal 10.

The root cause is that the 4.x branch processes the custom ID through Html::cleanCssIdentifier() without overriding the default character replacement map, which includes _ → - by default. The CSS class field has a built-in "Filter to HTML Clean CSS Identifier" configuration option that allows overriding this map — however, no equivalent override exists for the ID field.

Steps to reproduce

1. Install block_class 4.0.2 on Drupal 11
2. Place any block on a page
3. In the block configuration, enable "Customize the unique HTML ID of this block"
4. Enter an ID containing underscores, e.g. more_to_explore
5. Save the block
6. View the page and inspect the rendered HTML source

Expected result: The block renders with id="more_to_explore"

Actual result: The block renders with id="more-to-explore"

Proposed resolution

In BlockClassHelperService.php, change the Html::cleanCssIdentifier() call that processes the custom block ID to pass an explicit replacement map as the second argument. The map should omit the default _ → - mapping so underscores are preserved in the output:

// Before
Html::cleanCssIdentifier($custom_id)

// After
Html::cleanCssIdentifier($custom_id, [' ' => '-', '/' => '-', '[' => '-', ']' => ''])

Remaining tasks

- [ ] Review and test the patch
- [ ] Confirm fix works across block types (content blocks, views blocks, custom blocks)
- [ ] Automated test coverage for ID with underscores

User interface changes

None.

API changes

None.

Data model changes

None.