feat(text-editor): add highlight, subscript, superscript and mathematics toolbar actions

[ComputerCrack]

Adds four text formatting actions to the editor toolbar.

Highlight (@tiptap/extension-highlight)

• The extension was already part of the editor kit but had no toolbar button or command wired up; this simply exposes the existing functionality
• Toggles background highlight on selected text (single color mode)

Subscript / Superscript (@tiptap/extension-subscript, @tiptap/extension-superscript)

• Replaced hand-coded inconsistent SVG icons with Material Design Icons (Apache 2.0, 24×24) for visual consistency with the rest of the toolbar
• Fixed toolbar order — subscript and superscript are now grouped together instead of being separated by the text color button

Mathematics (@tiptap/extension-mathematics + KaTeX)

• Inline math via $...$ and block math via $$...$$
• Custom rendering plugin replaces the upstream library implementation to support multi-line math expressions (Shift+Enter / hardBreak within a single paragraph)
• Toggle behavior: wraps selection or inserts placeholder; pressing the button again unwraps
• Active state detection for both inline and block variants
• Math expressions inside code blocks are intentionally not rendered
• LaTeX paste handling: pasted text containing $...$ or $$...$$ is inserted as plain text, preserving the math delimiters

All actions include active state detection (button highlights when formatting is active at cursor position).

Note on pre-existing issues

The following ESLint (strict-boolean-expressions) errors exist on develop and are unrelated to this PR:

• plugins/text-editor-resources/src/components/extension/emoji.ts
• plugins/text-editor-resources/src/components/extension/reference.ts
• plugins/text-editor-resources/src/components/table/refreshTable.ts

[huly-github-staging]

Connected to Huly®: UBERF-15853

[ComputerCrack]

@aonnikov @BykhovDenis @ArtyomSavchenko Requesting manual review

[ArtyomSavchenko]

Hi @ComputerCrack,
Thanks for your contribution.
The validation build step failed with the following errors:

Error: /home/runner/work/platform/platform/plugins/text-editor-resources/src/kits/editor-kit.ts(83,7): error TS2742: The inferred type of 'StaticEditorKit' cannot be named without a reference to '../../../../foundations/core/packages/text/node_modules/@tiptap/extension-subscript/dist'. This is likely not portable. A type annotation is necessary.
Error: /home/runner/work/platform/platform/plugins/text-editor-resources/src/kits/editor-kit.ts(83,7): error TS2742: The inferred type of 'StaticEditorKit' cannot be named without a reference to '../../../../foundations/core/packages/text/node_modules/@tiptap/extension-superscript/dist'. This is likely not portable. A type annotation is necessary.

Could you please take a look?
For local verification, you can run rush validate to validate all packages, or rushx validate from the package folder to validate one package.