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]>

package.json

@@ -54,6 +54,7 @@
         "@tiptap/react": "3.32.0",
         "@tiptap/starter-kit": "3.32.0",
         "ace-builds": "^1.44.0",
+        "chart.js": "^4.6.1",
         "dayjs": "^1.11.23",
         "gray-matter": "^4.0.3",
         "html-to-react": "^1.7.0",
@@ -61,6 +62,7 @@
         "lucide-react": "^1.59.0",
         "mammoth": "^1.12.1",
         "mdx": "^0.3.1",
+        "mermaid": "^12.2.0",
         "next-mdx-remote": "^6.0.0",
         "nodemailer": "^9.0.5",
         "openai": "^7.4.0",