fix(KB-186): add ID-based tiebreaker to sort comparators for stable ordering

- Add numeric ID tiebreaker to TaskStore.listTasks() when createdAt timestamps match
- Add same tiebreaker to InlineCreateCard and TaskDetailModal dependency dropdown sorts
- Add store-sort integration test verifying ascending ID order with identical timestamps
- Add InlineCreateCard tests for identical-timestamp dropdown ordering and search filtering
- Add TaskDetailModal test for identical-timestamp dependency dropdown ordering

packages/core/src/__tests__/store-sort.test.ts

@@ -0,0 +1,55 @@
+import { describe, it, expect, beforeEach, afterEach } from "vitest";
+import { TaskStore } from "../store.js";
+import { rm } from "node:fs/promises";
+import { join } from "node:path";
+import { mkdtempSync } from "node:fs";
+import { tmpdir } from "node:os";
+
+function makeTmpDir(): string {
+  return mkdtempSync(join(tmpdir(), "kb-store-sort-test-"));
+}
+
+describe("TaskStore.listTasks() sort order", () => {
+  let rootDir: string;
+  let store: TaskStore;
+
+  beforeEach(async () => {
+    rootDir = makeTmpDir();
+    store = new TaskStore(rootDir);
+    await store.init();
+  });
+
+  afterEach(async () => {
+    store.stopWatching();
+    await rm(rootDir, { recursive: true, force: true });
+  });
+
+  it("returns tasks with identical createdAt in ascending ID order", async () => {
+    // Create three tasks — they may get the same createdAt if created fast enough
+    const t1 = await store.createTask({ description: "Task one" });
+    const t2 = await store.createTask({ description: "Task two" });
+    const t3 = await store.createTask({ description: "Task three" });
+
+    // Force identical createdAt by rewriting the task.json files
+    const { readFile, writeFile } = await import("node:fs/promises");
+    const tasksDir = join(rootDir, ".kb", "tasks");
+    const sameTimestamp = "2026-06-01T00:00:00Z";
+
+    for (const t of [t1, t2, t3]) {
+      const jsonPath = join(tasksDir, t.id, "task.json");
+      const data = JSON.parse(await readFile(jsonPath, "utf-8"));
+      data.createdAt = sameTimestamp;
+      data.updatedAt = sameTimestamp;
+      await writeFile(jsonPath, JSON.stringify(data, null, 2));
+    }
+
+    const tasks = await store.listTasks();
+    const ids = tasks.map((t) => t.id);
+
+    // Should be ascending by numeric ID portion
+    const nums = ids.map((id) => parseInt(id.slice(id.lastIndexOf("-") + 1), 10));
+    for (let i = 1; i < nums.length; i++) {
+      expect(nums[i]).toBeGreaterThan(nums[i - 1]);
+    }
+  });
+});