refactor(zalouser): share offset-preserving text chunk ranges (#105842)

* refactor(zalouser): share text chunk ranges

* chore(plugin-sdk): refresh combined API baseline

src/plugin-sdk/text-chunking.test.ts

@@ -2,7 +2,7 @@
  * Tests text and Markdown chunking helpers exported by the plugin SDK.
  */
 import { describe, expect, it } from "vitest";
-import { chunkTextForOutbound } from "./text-chunking.js";
+import { chunkTextForOutbound, chunkTextRanges } from "./text-chunking.js";
 
 describe("chunkTextForOutbound", () => {
   it.each([
@@ -28,3 +28,44 @@ describe("chunkTextForOutbound", () => {
     expect(chunkTextForOutbound(text, maxLen)).toEqual(expected);
   });
 });
+
+describe("chunkTextRanges", () => {
+  it("returns contiguous hard ranges without dropping whitespace", () => {
+    const text = "alpha  beta\n\ngamma delta";
+    const ranges = chunkTextRanges(text, { limit: 12, mode: "hard" });
+
+    expect(ranges).toEqual([
+      { start: 0, end: 12 },
+      { start: 12, end: 24 },
+    ]);
+    expect(ranges.map(({ start, end }) => text.slice(start, end))).toEqual([
+      "alpha  beta\n",
+      "\ngamma delta",
+    ]);
+  });
+
+  it("prefers paragraph, newline, then whitespace boundaries", () => {
+    const text = "a\n\nb\nc xyz";
+    const ranges = chunkTextRanges(text, { limit: 8, mode: "preferred" });
+
+    expect(ranges.map(({ start, end }) => text.slice(start, end))).toEqual(["a\n\n", "b\nc xyz"]);
+  });
+
+  it("falls back to hard ranges and handles empty or non-positive limits", () => {
+    expect(chunkTextRanges("abcdefgh", { limit: 3, mode: "preferred" })).toEqual([
+      { start: 0, end: 3 },
+      { start: 3, end: 6 },
+      { start: 6, end: 8 },
+    ]);
+    expect(chunkTextRanges("", { limit: 3 })).toEqual([]);
+    expect(chunkTextRanges("abc", { limit: 0 })).toEqual([{ start: 0, end: 3 }]);
+  });
+
+  it.each(["hard", "preferred"] as const)("keeps surrogate pairs intact in %s mode", (mode) => {
+    expect(chunkTextRanges("a😀b", { limit: 2, mode })).toEqual([
+      { start: 0, end: 1 },
+      { start: 1, end: 3 },
+      { start: 3, end: 4 },
+    ]);
+  });
+});

src/plugin-sdk/text-chunking.ts

@@ -1,6 +1,13 @@
 // Text chunking helpers split long outbound text while preserving readable line boundaries.
 import { chunkTextByBreakResolver } from "../shared/text-chunking.js";
 
+/** Offset-preserving text ranges for transports with native style metadata. */
+export {
+  chunkTextRanges,
+  type ChunkTextRangesOptions,
+  type TextChunkRange,
+} from "../../packages/markdown-core/src/chunk-text.js";
+
 /**
  * Splits outbound channel text into chunks no longer than the requested limit.
  * Newline boundaries win over spaces; text without usable separators falls back