Add bot graphics

Bots can now show a concept as a visual: create_graphic (with
update_graphic, read_graphic and list_graphics, on every run, no computer
needed) stores one HTML document in bot_graphics, per user like the
conversation, and the chat renders its [graphic:ID] ref as an inline card
sized to fit, with a large view and a page of its own (no rail).

Graphic HTML is treated as hostile: it is only served at /graphics/<id>
with a CSP sandbox allowing scripts under an origin of its own and no
network, loading only the vendored Chart.js and Mermaid from
/graphics-lib/. The document carries the app's theme vars and scrollbars,
reports its height to the thread, and a frame that navigates away is
closed.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/data/app-data.ts

@@ -535,6 +535,15 @@ export const AppData = {
      * themselves to a reply; older ones are named.
      */
     BotReplyAttachmentMessages: 4,
+    /**
+     * Longest HTML document a bot graphic (`bot_graphics`) may be.
+     */
+    BotGraphicMaxChars: 200000,
+    /**
+     * Tallest a graphic grows inline in the thread (px) before it scrolls
+     * inside its frame.
+     */
+    BotGraphicInlineMaxHeight: 640,
     /**
      * Longest dictation the composer records before it stops on its own.
      */