Integrate with the MDX editor

I think this ticket should be to provide a function in a DocumentLoaderManager service to convert getToolInputSchema into Drupal fields, similar to how AI tool + explorer works.

I think all the logic is on the explorer form; we could move it into the service.

This way, we could fix both of the issues in one singular code logic, and other integrations in the future will be bulletproof as well.

Also, I think the best approach is to have MDX logic in a sub-module similar to fwa and tool modules. We could also include ck-editor integration as well

I really like this feature, super useful! I've left some comments regarding the JS/MDXEditor part of the implementation :)

Tys, bbruno and nick for the work.
I fixed all issues mentioned by bbruno. Additionally, I fixed;

1. Button stays visible in diff/source mode

Because the "Load document" button is imperatively injected into the DOM (outside React), it was not removed when the MDX editor switches to diff or source mode — the DiffSourceToggleWrapper only manages its own React children. Fixed by adding a second MutationObserver on the toolbar that detects mode changes (by checking for the toolbarTitleMode class) and hides the button with display: none when in an alternate mode. Uses a disconnect/reconnect pattern to avoid infinite loops when mutating the DOM inside the observer callback.

2. Button appears first instead of last when switching back to rich-text mode

When switching from diff/source back to rich-text mode, React re-renders all toolbar children as new DOM nodes. Our imperatively injected button was still at its old position, which put it before the newly rendered buttons — making it appear first in the toolbar. Fixed by re-positioning the button with toolbar.insertBefore(button, toolbar.lastElementChild) each time rich-text mode is restored, so it always sits just before the diff/source toggle group at the end.

3. Tooltip styling doesn't match native toolbar tooltips

The native MDX editor toolbar buttons use @radix-ui/react-tooltip (via a TooltipWrap component) which renders styled floating tooltips via React portals. Since our button is injected imperatively outside React, it cannot use the Radix tooltip component. A plain title attribute produces a browser-native tooltip that looks completely different. Fixed by creating a custom DOM-based tooltip (.dl-mdx-tooltip) that appears on mouseenter with a 100ms delay (matching Radix's delayDuration), positioned 10px above the button (matching Radix's sideOffset), using the same CSS custom properties as the native _tooltipContent class: --baseText for background, --baseBase for text color, --radius-medium for border-radius, --text-xs for font-size. The tooltip is dismissed on mouseleave and on click.

I created a separate branch that dynamically loads the loaders, meaning you can load context from anywhere you want, not only files, and it includes the media widget, which I think is more user-friendly than what we currently have.

Added this as a related issue to the ccc meta: #3569310: [META] Context source plugin feature (context from PDF/MD/Word/URL/etc)