test(app): 補齊 isSafeRepoPath/extractBalancedJSON/normalizeText/repairJSONArrayWithAI/格式化函式測試

為可測性 export 三個內部函式（isSafeRepoPath、extractBalancedJSON/extractJSONText、normalizeText）。

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/test/llm.test.js

@@ -1,6 +1,7 @@
 import { describe, it, beforeEach, afterEach, mock } from 'node:test';
 import assert from 'node:assert/strict';
 import axios from 'axios';
+import { extractBalancedJSON, extractJSONText } from '../llm.js';
 
 const ENV_KEYS = [
   'OPENCODE_BASE_URL', 'OPENCODE_MODEL', 'OPENCODE_PROVIDER',
@@ -143,3 +144,90 @@ describe('chatJSON', async () => {
     assert.deepEqual(result, []);
   });
 });
+
+describe('extractBalancedJSON', () => {
+  it('returns the whole object for a simple object from index 0', () => {
+    const text = '{"a":1}';
+
+    assert.equal(extractBalancedJSON(text, 0), '{"a":1}');
+  });
+
+  it('returns the full balanced segment for deeply nested object/array', () => {
+    const text = '{"a":[1,{"b":[2,{"c":3}]}],"d":4}';
+
+    assert.equal(extractBalancedJSON(text, 0), '{"a":[1,{"b":[2,{"c":3}]}],"d":4}');
+  });
+
+  it('does not let braces inside a string value break balancing', () => {
+    const text = '{"a":"}{"}';
+
+    assert.equal(extractBalancedJSON(text, 0), '{"a":"}{"}');
+  });
+
+  it('handles an escaped quote inside a string value', () => {
+    const text = '{"a":"\\""}';
+
+    assert.equal(extractBalancedJSON(text, 0), '{"a":"\\""}');
+  });
+
+  it('returns null for truncated/incomplete JSON', () => {
+    const text = '{"a":1';
+
+    assert.equal(extractBalancedJSON(text, 0), null);
+  });
+
+  it('extracts a balanced array when starting at a "["', () => {
+    const text = '[1,[2,3],{"a":4}]';
+
+    assert.equal(extractBalancedJSON(text, 0), '[1,[2,3],{"a":4}]');
+  });
+
+  it('excludes trailing content after the balanced segment', () => {
+    const text = '{"a":1} trailing text {"b":2}';
+
+    assert.equal(extractBalancedJSON(text, 0), '{"a":1}');
+  });
+});
+
+describe('extractJSONText', () => {
+  it('strips a fenced ```json block', () => {
+    const text = '```json\n{"a":1}\n```';
+
+    const result = extractJSONText(text);
+
+    assert.deepEqual(JSON.parse(result), { a: 1 });
+  });
+
+  it('extracts a JSON object after leading prose', () => {
+    const text = 'Here are the findings:\n{"level":"critical"}';
+
+    const result = extractJSONText(text);
+
+    assert.deepEqual(JSON.parse(result), { level: 'critical' });
+  });
+
+  it('extracts an array embedded in surrounding text', () => {
+    const text = 'prefix [1,2,3] suffix';
+
+    const result = extractJSONText(text);
+
+    assert.deepEqual(JSON.parse(result), [1, 2, 3]);
+  });
+
+  it('returns an already-pure JSON string as-is', () => {
+    const text = '{"a":1,"b":[2,3]}';
+
+    const result = extractJSONText(text);
+
+    assert.equal(result, '{"a":1,"b":[2,3]}');
+    assert.deepEqual(JSON.parse(result), { a: 1, b: [2, 3] });
+  });
+
+  it('returns the de-fenced original text when no valid JSON is found', () => {
+    const text = '```\nnot json at all\n```';
+
+    const result = extractJSONText(text);
+
+    assert.equal(result, 'not json at all');
+  });
+});