Allow bold and underline formatting for individual words within a text element

Excalidraw's text elements currently support only a single, uniform style (font family, weight, decoration) applied to the entire block. There's no way to make individual words or a range of characters bold or underlined within the same text element.

Current behavior: Text formatting options apply to the whole text element — no inline/partial formatting is possible.

Expected behavior: Allow selecting a word or range of text within a text element and applying bold and/or underline just to that selection, similar to standard rich-text editors.

Workaround: Currently the only way to emphasize part of a sentence is to split it into separate text elements with different styles and manually align them, which is fragile and breaks if the text needs to be edited later.

Related: This ties into the broader need for per-word/per-character styling (color, bold, underline) within a single text element