feat(intelligence): add lexical briefing text helpers

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/lib/intelligence/briefingText.ts

@@ -0,0 +1,84 @@
+interface LexicalTextNode {
+  type: string;
+  text?: unknown;
+  children?: unknown[];
+}
+
+interface LexicalBlock {
+  type: string;
+  children?: unknown[];
+}
+
+export type SerializedLexicalState = {
+  root: {
+    type: "root";
+    children: {
+      type: "paragraph";
+      children: { type: "text"; text: string; version: number }[];
+      direction: null;
+      format: "";
+      indent: number;
+      version: number;
+    }[];
+    direction: "ltr" | "rtl" | null;
+    format: "left" | "start" | "center" | "right" | "end" | "justify" | "";
+    indent: number;
+    version: number;
+  };
+};
+
+function collectText(node: unknown): string {
+  if (typeof node !== "object" || node === null) return "";
+  const n = node as LexicalTextNode;
+  if (n.type === "linebreak") return "\n";
+  if (typeof n.text === "string") return n.text;
+  if (!Array.isArray(n.children)) return "";
+  return n.children.map(collectText).join("");
+}
+
+function collectBlockText(node: unknown): string {
+  if (typeof node !== "object" || node === null) return "";
+  const n = node as LexicalBlock;
+  if (!Array.isArray(n.children)) return "";
+  return n.children.map(collectText).join("");
+}
+
+export function lexicalToText(details: unknown): string {
+  if (typeof details !== "object" || details === null) return "";
+  const root = (details as SerializedLexicalState).root;
+  if (!root || !Array.isArray(root.children)) return "";
+  return root.children
+    .map(collectBlockText)
+    .filter((line, i, all) => line.trim() !== "" || (i > 0 && i < all.length - 1))
+    .join("\n");
+}
+
+export function textToLexical(text: string): SerializedLexicalState {
+  const lines = text.split("\n");
+  return {
+    root: {
+      type: "root",
+      children: (lines.length > 0 ? lines : [""]).map((line) => ({
+        type: "paragraph",
+        children:
+          line === ""
+            ? []
+            : [
+                {
+                  type: "text",
+                  text: line,
+                  version: 1,
+                },
+              ],
+        direction: null,
+        format: "",
+        indent: 0,
+        version: 1,
+      })),
+      direction: "ltr",
+      format: "",
+      indent: 0,
+      version: 1,
+    },
+  };
+}