Replace the composer textarea with a Tiptap markdown editor

The composer now writes markdown with bold, italic, strike, code,
links, quotes and lists, from shortcuts, markdown typing or a bubble
over the selection. @ mentions a bot and # a workspace, shown as chips
and saved as [bot:ID] / [workspace:ID]. Text selected in a message can
be quoted into the composer. User messages render as markdown, and
replies tell the bot who and what the user mentioned.

Adds an ESM stand-in for use-sync-external-store, since bunext keeps
React external in page bundles and the CommonJS original requires it.

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

src/pages/admin/bots/[bot_id]/(partials)/markdown-link.tsx

@@ -1,15 +1,22 @@
 import type { ComponentProps } from "react";
 import Link from "@moduletrace/twui/layout/Link";
 import { ComputerViewModes, type ComputerViewMode } from "@/src/dict/computer-dict";
-import { BotRefHrefPrefix, ComputerRefHrefPrefix, TakeOverRefHrefPrefix } from "@/src/utils/link-computer-refs";
+import {
+    BotRefHrefPrefix,
+    ComputerRefHrefPrefix,
+    TakeOverRefHrefPrefix,
+    WorkspaceRefHrefPrefix,
+} from "@/src/utils/link-computer-refs";
 import BotRefChip from "./bot-ref-chip";
 import ComputerRefChip from "./computer-ref-chip";
 import TakeOverChip from "./take-over-chip";
+import WorkspaceRefChip from "./workspace-ref-chip";
 
 /**
  * A link in a bot message. A computer the bot named (`linkComputerRefs`)
  * becomes its switch button, a take-over request a button that opens the
- * computer, a bot it named a link to that bot's conversation; anything else opens in a new tab.
+ * computer, a bot it named a link to that bot's conversation, a workspace
+ * a link to that workspace; anything else opens in a new tab.
  */
 export default function MarkdownLink({ href, children }: ComponentProps<"a">) {
     if (href?.startsWith(ComputerRefHrefPrefix)) {
@@ -39,6 +46,12 @@ export default function MarkdownLink({ href, children }: ComponentProps<"a">) {
         if (bot_id) return <BotRefChip bot_id={bot_id} />;
     }
 
+    if (href?.startsWith(WorkspaceRefHrefPrefix)) {
+        const workspace_id = Number(href.slice(WorkspaceRefHrefPrefix.length));
+
+        if (workspace_id) return <WorkspaceRefChip workspace_id={workspace_id} />;
+    }
+
     return (
         <Link
             href={href}