allozaur/feat/chat form contenteditable (#26717)

* feat: Add contenteditable tokenizer for badge/code-chip chat input

* feat: Add source-space undo/redo history for the rich input

* feat: Split text glued to a closing code fence onto its own line

* feat: Add ChatFormContenteditable rich input renderer

* feat : wire the contenteditable into ChatForm with auto-switch gating

tools/ui/tests/client/components/ChatFormTestWrapper.svelte

@@ -0,0 +1,12 @@
+<script lang="ts">
+	import * as Tooltip from '$lib/components/ui/tooltip';
+	import ChatForm from '$lib/components/app/chat/ChatForm/ChatForm.svelte';
+
+	let { onSubmit }: { onSubmit?: () => void } = $props();
+
+	let value = $state('');
+</script>
+
+<Tooltip.Provider>
+	<ChatForm bind:value {onSubmit} />
+</Tooltip.Provider>