docs(toolbar): clarify how fonts work in SuperDoc (#2848)

* docs(toolbar): clarify how fonts work in SuperDoc

A .docx carries font names, not font data. Consumers often hit this
when a document uses Cambria/Calibri/Aptos and the rendered text
falls back to Helvetica in the browser. The existing docs were an
empty redirect stub plus an inaccurate Info callout that claimed
imported DOCX fonts auto-populate the toolbar dropdown (they don't).

Rewrites the Font support getting-started page and the toolbar
Font configuration section to separate two concerns cleanly:
registration (selectability via `fonts`) vs. loading (real glyphs
via `@font-face`). Adds a working alias example and a table of
metric-compatible free substitutes for Office fonts.

* docs(getting-started): keep fonts page as redirect stub

Revert the expanded font-support page back to the one-line redirect
stub. The real content already lives in the toolbar Font configuration
section — the stub only needs the redirect target corrected from
`/modules/toolbar#font-configuration` (which bounces to overview and
has no matching anchor) to `/modules/toolbar/built-in#font-configuration`.

Author: caio-pizzol

apps/docs/getting-started/fonts.mdx

@@ -2,6 +2,6 @@
 title: Font Support
 ---
 
-Loading toolbar <a href="/modules/toolbar#font-configuration">font config</a>...
+Loading toolbar <a href="/modules/toolbar/built-in#font-configuration">font config</a>...
 
-{(() => { window.location.href = '/modules/toolbar#font-configuration'; })()}
+{(() => { window.location.href = '/modules/toolbar/built-in#font-configuration'; })()}

apps/docs/modules/toolbar/built-in.mdx

@@ -323,24 +323,22 @@ Icons should be 24x24 viewBox SVGs with `fill="currentColor"` for proper theming
 
 ## Font configuration
 
+The toolbar dropdown lists only what you register in `fonts`. Imported documents don't auto-populate the list — if a user opens a `.docx` that uses Cambria and Cambria isn't registered, the current-selection indicator shows "Cambria" but the user can't pick it from the dropdown.
+
 <ParamField path="fonts" type="Array">
   <Expandable title="Font object properties">
     <ParamField path="label" type="string" required>
-      Display name
+      Display name shown in the dropdown
     </ParamField>
     <ParamField path="key" type="string" required>
-      Font-family CSS value
+      Font-family CSS value applied to text
     </ParamField>
     <ParamField path="fontWeight" type="number">
       Font weight
     </ParamField>
   </Expandable>
 </ParamField>
 
-<Info>
-SuperDoc does not load fonts automatically. Custom fonts from imported DOCX files will display in the toolbar, but won't be selectable unless you load them in your application (via CSS `@font-face`, Google Fonts, etc.) and add them to the `fonts` array.
-</Info>
-
 ```javascript
 fonts: [
   { label: 'Arial', key: 'Arial' },
@@ -349,6 +347,55 @@ fonts: [
 ]
 ```
 
+<Info>
+  Registering a font in `fonts` makes it **selectable**. It doesn't load any font files. To make the font actually render with its real glyphs, load it on your host page via `@font-face` or a `<link>` to a font service. Fonts the browser can't find fall back to the CSS generic.
+</Info>
+
+### Loading web fonts
+
+Any font loaded on your host page is available inside the editor. Load it, then register it in `fonts`:
+
+```html
+<link rel="stylesheet" href="https://fonts.googleapis.com/css2?family=Inter&display=swap" />
+```
+
+```javascript
+modules: {
+  toolbar: {
+    fonts: [{ label: 'Inter', key: 'Inter, sans-serif' }]
+  }
+}
+```
+
+### Substituting Microsoft Office fonts
+
+Most `.docx` files use Cambria, Calibri, or Aptos — fonts bundled with Word on desktop but not present in browsers. Google hosts free metric-compatible replacements:
+
+| Office font | Free substitute | Notes |
+|---|---|---|
+| Calibri | [Carlito](https://fonts.google.com/specimen/Carlito) | Sans-serif, metric-identical — designed as a direct drop-in |
+| Cambria | [Tinos](https://fonts.google.com/specimen/Tinos) or [Gelasio](https://fonts.google.com/specimen/Gelasio) | Serif |
+| Aptos | [Carlito](https://fonts.google.com/specimen/Carlito) or [Inter](https://fonts.google.com/specimen/Inter) | Sans-serif — no free metric-identical match exists yet |
+
+Download the `.woff2` files from Google Fonts, host them with your app, and alias each substitute to the original Word name via `@font-face`. The browser will then render real Carlito/Tinos glyphs whenever the document asks for Calibri/Cambria — no document or SuperDoc changes needed.
+
+```html
+<style>
+  @font-face {
+    font-family: 'Calibri';
+    src: url('/fonts/Carlito-Regular.woff2') format('woff2');
+    font-display: swap;
+  }
+  @font-face {
+    font-family: 'Cambria';
+    src: url('/fonts/Tinos-Regular.woff2') format('woff2');
+    font-display: swap;
+  }
+</style>
+```
+
+Self-hosting the `.woff2` files is more reliable than linking to Google Fonts CDN URLs directly — those URLs change when Google updates a font version.
+
 ## Responsive behavior
 
 The toolbar adapts at these widths: