fix(yuanbao-adapter): correct fragment merge and json candidate parsing

Stop dropping short repeated fragments in mergeText (append them unless
the duplicate is long enough to be a real echo) and drop the unreliable
reverse-overlap branch. Return early from extractJSONCandidates when the
whole body parses, and drop the seen-set so line-level frames are no
longer deduped away.

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

apps/desktop-client/src/main/adapters/yuanbao.test.ts

@@ -69,6 +69,36 @@ describe('yuanbao adapter helpers', () => {
     expect(mergeText(first, repeated)).toBe(repeated)
   })
 
+  it('preserves repeated Markdown tokens from incremental SSE frames', () => {
+    const fragments = [
+      '### 推荐清单\n\n- **',
+      '拾光里',
+      '**：本地工厂',
+      '\n- **',
+      '欧派',
+      '**：全国连锁',
+      '\n\n1. **',
+      '看板材',
+      '**',
+      '\n2. **',
+      '看封边',
+      '**',
+    ]
+
+    const summary = parseYuanbaoCaptures([
+      {
+        url: 'https://yuanbao.tencent.com/api/chat/conversation-markdown',
+        status: 200,
+        contentType: 'text/event-stream',
+        body: fragments.map((msg) => `data: ${JSON.stringify({ type: 'text', msg })}`).join('\n\n'),
+      },
+    ])
+
+    expect(summary.answer).toBe(
+      '### 推荐清单\n\n- **拾光里**：本地工厂\n- **欧派**：全国连锁\n\n1. **看板材**\n2. **看封边**',
+    )
+  })
+
   it('keeps a valid API SSE answer even when the DOM fallback is longer', () => {
     const apiAnswer =
       '### 核心结论\n\n混动车兼顾补能效率与低速油耗。\n\n- 适合长途出行\n- 适合没有固定充电桩的用户'

apps/desktop-client/src/main/adapters/yuanbao.ts

@@ -426,8 +426,8 @@ function mergeText(current: string | null, nextFragment: string | null): string
   if (!current) {
     return nextFragment
   }
-  if (current === nextFragment || current.includes(nextFragment)) {
-    return current
+  if (current === nextFragment) {
+    return nextFragment.length >= 16 ? current : `${current}${nextFragment}`
   }
   if (nextFragment.startsWith(current)) {
     return nextFragment
@@ -438,11 +438,6 @@ function mergeText(current: string | null, nextFragment: string | null): string
     return `${current}${nextFragment.slice(forwardOverlap)}`
   }
 
-  const reverseOverlap = sharedBoundaryLength(nextFragment, current)
-  if (reverseOverlap > 0) {
-    return `${nextFragment}${current.slice(reverseOverlap)}`
-  }
-
   const commonPrefixLength = sharedPrefixLength(current, nextFragment)
   const duplicatePrefixThreshold = Math.max(
     16,
@@ -978,22 +973,24 @@ function attachYuanbaoResponseCapture(
 
 function extractJSONCandidates(body: string): unknown[] {
   const values: unknown[] = []
-  const seen = new Set<string>()
 
-  const pushParsed = (raw: string) => {
+  const pushParsed = (raw: string): boolean => {
     const normalized = raw.trim()
-    if (!normalized || seen.has(normalized)) {
-      return
+    if (!normalized) {
+      return false
     }
     try {
       values.push(JSON.parse(normalized))
-      seen.add(normalized)
+      return true
     } catch {
       // Ignore malformed frames and continue with the remaining candidates.
+      return false
     }
   }
 
-  pushParsed(body)
+  if (pushParsed(body)) {
+    return values
+  }
 
   for (const rawLine of body.split(/\r?\n/)) {
     const line = rawLine.trim()