feat: 階段二 - Findings 產生與合併

- app/findings.js: 各角色分析 diff、讀取舊 findings、合併去重、等級排序
- app/main.js: 實作 Step2/Step3，log findings 統計

app/findings.js

@@ -0,0 +1,63 @@
+import fs from 'fs';
+import path from 'path';
+import { chatJSON } from './llm.js';
+import { FINDINGS_PATH } from './config.js';
+
+const LEVELS = ['critical', 'warning', 'info'];
+
+/**
+ * 用單一角色分析 diff，回傳 findings 陣列
+ */
+export async function analyzeWithRole(role, diff) {
+  console.log(`  [${role.name}] 開始分析...`);
+  const findings = await chatJSON(role.system_prompt, `以下是 Git Diff 內容：\n\n${diff}`);
+  // 確保每筆都有必要欄位，並標記為新問題
+  const valid = findings.filter(f => f.level && f.role && f.location && f.suggestion)
+    .map(f => ({ ...f, is_new: true }));
+  console.log(`  [${role.name}] 找到 ${valid.length} 個問題`);
+  return valid;
+}
+
+/**
+ * 讀取舊 findings（從 workspace 的 FINDINGS_PATH）
+ */
+export function loadOldFindings(workspace) {
+  const fullPath = path.join(workspace, FINDINGS_PATH);
+  if (!fs.existsSync(fullPath)) {
+    console.log('  舊 findings 檔案不存在，視為空');
+    return [];
+  }
+  try {
+    const data = JSON.parse(fs.readFileSync(fullPath, 'utf8'));
+    const old = (Array.isArray(data) ? data : []).map(f => ({ ...f, is_new: false }));
+    console.log(`  讀取舊 findings: ${old.length} 筆`);
+    return old;
+  } catch (e) {
+    console.log(`  ⚠️  讀取舊 findings 失敗: ${e.message}，視為空`);
+    return [];
+  }
+}
+
+/**
+ * 合併新舊 findings，以 (role + location + suggestion前50字) 為 key 去除重複
+ * 舊問題保留，新問題若與舊問題重複則捨棄
+ */
+export function mergeFindings(oldFindings, newFindings) {
+  const key = f => `${f.role}|${f.location}|${String(f.suggestion).slice(0, 50)}`;
+  const seen = new Set(oldFindings.map(key));
+  const deduped = newFindings.filter(f => {
+    if (seen.has(key(f))) return false;
+    seen.add(key(f));
+    return true;
+  });
+  const merged = [...oldFindings, ...deduped];
+  console.log(`  合併結果: 舊=${oldFindings.length} 新(去重後)=${deduped.length} 總計=${merged.length}`);
+  return merged;
+}
+
+/**
+ * 依等級排序（critical > warning > info）
+ */
+export function sortByLevel(findings) {
+  return [...findings].sort((a, b) => LEVELS.indexOf(a.level) - LEVELS.indexOf(b.level));
+}