fix: remove zwsp unicode usage across themes

[epetrow]

closes: #5639

Overview

The usage of unicode characters has intermittently caused issues with strange looking charactes sometimes being displayed. At the moment this can be observed when using the themes from unpkg, where the problem is related to encoding. Since we are minifying the all.css file and relying on SASS's --style=compressed option to do so the @charset declaration at the top of the file is being removed (which is stardard behaviour). The problem stems from the lack of charset in the content-type header of the files from unpkg, but we do not seem to have control over that.

\200b unicode usage patterns

There are two main usage patters for the zero-width space unicode character at the moment:

1. Wrapper elements (checkbox-wrap, radio-wrap, icon-wrap) - Use ::before with \200b to establish minimum height for flex containers
2. Text elements (input-value-text, list-item-text, window-title) - Use ::before or &:empty::before with \200b to prevent collapse

What has been tried

1. Simply removing the unicode character is not a solution because the outlined usage patters break and there are visual degradations. The same can be said about replacing \200b with a simple space " "
2. Release CSS files that contain "\200b" rather than a special invisible character - We can tell SASS not to parse the zero-width space character and escape it with \\200b however this would cause the literal characters \200b to be displayed.
3. Set explicit height equal to the calculated line height: This could work, but we should probably use the lh unit instead of calculating the line height ourselves (e.g. var(--kendo-font-size) * var(--kendo-line-height). I have tried the second approach and there are some edge cases that are tricky and in general it does not seem like a good solution since if someone customizes either of these css variables the content will shift (e.g. checkboxes inside ActionSheet).
4. Explicitly add @charset after minification - We could have some script or use a tool like PostCSS to add the @charset that is being stripped, but that needs to be tested after we ship the css files to unpkg.

[github-actions]

Packages Report

	core	default	classic	bootstrap	material	fluent	utils	html
Size	29.20 KB (0.0%)	769.53 KB (0.0%🔼)	768.24 KB (0.0%🔼)	783.02 KB (0.0%🔼)	916.25 KB (0.0%🔼)	1181.63 KB (0.0%🔼)	625.19 KB (0.0%)	77.78 MB (0.0%)
Gzip Size	4.85 KB (0.0%)	99.38 KB (0.0%)	99.62 KB (-0.0%🔽)	101.32 KB (-0.0%🔽)	112.31 KB (-0.0%🔽)	136.80 KB (0.0%)	52.16 KB (0.0%)	15.95 MB (0.0%)
Compile Time	0.9 s (0.0%)	3.0 s (0.0%)	3.1 s (0.0%)	2.9 s (0.0%)	3.1 s (0.0%)	3.6 s (0.0%)	2.7 s (0.0%)	8.5 s (0.0%)

[Copilot]

Pull Request Overview

This PR removes the use of zero-width space (ZWSP) Unicode character (\200b) across theme components and replaces it with proper CSS height calculations to maintain layout consistency.

Key Changes

• Replaced all instances of content: "\200b" with content: ""
• Added explicit height calculations using font-size and line-height variables to preserve spacing behavior
• Fixed initialization of $kendo-input-sizes variable from null to empty map ()

Reviewed Changes

Copilot reviewed 15 out of 42 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
packages/core/scss/components/window/_layout.scss	Replaced ZWSP with explicit height calculation for empty window titles
packages/core/scss/components/timeselector/_layout.scss	Removed ZWSP from timeselector pseudo-elements
packages/core/scss/components/table/_layout.scss	Added height calculation and box-sizing for table group rows
packages/core/scss/components/skeleton/_layout.scss	Replaced ZWSP with inline-block display for skeleton text
packages/core/scss/components/radio/_layout.scss	Added height calculation for radio button wrapper
packages/core/scss/components/list/_layout.scss	Removed ZWSP from list elements
packages/core/scss/components/input/_variables.scss	Changed $kendo-input-sizes default from null to empty map
packages/core/scss/components/input/_layout.scss	Removed ZWSP from input value text
packages/core/scss/components/icons/_layout.scss	Added height calculation for icon wrapper
packages/core/scss/components/gantt/_layout.scss	Removed ZWSP from gantt table cells
packages/core/scss/components/dropdowntree/_layout.scss	Added size-specific height calculations for multiselecttree
packages/core/scss/components/column-menu/_layout.scss	Added height calculation for checkbox wrapper in column menu
packages/core/scss/components/checkbox/_layout.scss	Added height calculation for checkbox wrapper
packages/core/scss/components/calendar/_layout.scss	Removed ZWSP from calendar pseudo-elements
packages/core/scss/components/action-sheet/_layout.scss	Added height calculations for icon and checkbox wrappers