fix(version): 限制任务需求候选为版本已关联需求

apps/web/lib/requirement-selector.test.ts

@@ -1,7 +1,11 @@
 import test from 'node:test';
 import assert from 'node:assert/strict';
 
-import { getProjectAdoptedRequirementCandidates, mergeSelectedRequirementOptions } from './requirement-selector';
+import {
+  getProjectAdoptedRequirementCandidates,
+  getVersionLinkedRequirementCandidates,
+  mergeSelectedRequirementOptions,
+} from './requirement-selector';
 import type { Requirement } from './requirement';
 
 const base = {
@@ -38,6 +42,17 @@ test('returns only adopted requirements from current project', () => {
   assert.deepEqual(result.map((r: Requirement) => r.id), ['r1']);
 });
 
+test('returns only requirements already linked to current version', () => {
+  const result = getVersionLinkedRequirementCandidates([
+    req('r1', 'project-1', 'adopted'),
+    req('r2', 'project-1', 'developing'),
+    req('r3', 'project-1', 'adopted'),
+    req('r4', 'project-2', 'adopted'),
+  ], ['r2', 'r1']);
+
+  assert.deepEqual(result.map((r: Requirement) => r.id), ['r2', 'r1']);
+});
+
 test('keeps historical selected requirements as non-candidate options', () => {
   const options = mergeSelectedRequirementOptions(
     [req('r1', 'project-1', 'adopted')],