Pick up upstream sticky notes (excalidraw#12064) in the next @nextcloud/excalidraw bump

Problem

Whiteboard has no sticky note tool. To get the equivalent of a note, a user has to draw a rectangle, assign a background color, enter bound text, and then manually reduce the font size so the text fits. In a teaching session with students that is four steps too many, and it has to be explained before the first exercise can start.

This is already solved upstream

excalidraw/excalidraw#12064 (feat(editor): sticky notes) was merged into master on 2026-09-10 and closes excalidraw/excalidraw#9696, which was filed from the Nextcloud side.

It adds a dedicated stickynote element and tool (N):

• the text field is focused on creation — no extra keypress to start typing
• the font auto-fits: fontSizeMax is the user's ceiling, the effective fontSize is derived from it, and the note only grows past its base height once the text still overflows at the minimum font
• notes are their own color domain, so note colors don't fight the shape palette
• the element skeleton API supports { "type": "stickynote", x, y, label: { text, fontSize? } }

What's missing here

package.json pins @nextcloud/excalidraw to 0.18.0-6135eb0 (published 2026-05-12). The newest published fork snapshot, 0.18.0-fe2343d, also predates the merge. So the feature can only arrive with a fork rebase onto a master state that includes #12064.

Request

Please include #12064 in the scope of #1115 (bump and release nextcloud/excalidraw), and treat the stickynote element as something the file format and the collaboration backend need to round-trip. Happy to test on a production instance once a snapshot is available.

Context

We generate course whiteboards from a JSON spec into .whiteboard files. Notes are currently emitted as rectangle + bound text, with a non-empty placeholder text that exists purely to carry our typography — an empty bound text is discarded on load, and the one recreated on first keystroke picks up the tool defaults (20px) instead. We also ship an on-board usage hint telling participants to double-click a field rather than reach for the free text tool. A native stickynote would let all of that go away.

Start with package.json and the bump and release work in issue #1115, then verify that the fork snapshot includes upstream Excalidraw PR #12064. Review the existing .whiteboard JSON generation and collaboration round-trip paths; done means stickynote elements survive both without the rectangle-plus-bound-text workaround.