fix: Normalize text-wrapped agent result JSON

Some providers return the final Agent answer as a text block containing structured JSON instead of Markdown. The desktop result fallback now parses that text-wrapped shape and formats plain and grouped result arrays into readable Markdown before display.

Constraint: Historical sessions can store Agent tool_result content as [{ type: 'text', text: '{...}' }] rather than a direct object
Rejected: Treat provider-specific JSON output as a model bug only | existing transcripts still need readable display
Confidence: high
Scope-risk: narrow
Directive: Agent result display must normalize text-wrapped structured payloads before falling back to raw text
Tested: cd desktop && bun run test -- run src/components/chat/MessageList.test.tsx -t "formats structured agent fallback"
Tested: cd desktop && bun run test -- run src/components/chat/MessageList.test.tsx -t agent
Not-tested: Full desktop gate per request to avoid broad gate/test runs

desktop/src/components/chat/MessageList.test.tsx

@@ -1151,21 +1151,31 @@ describe('MessageList nested tool calls', () => {
               id: 'result-agent',
               type: 'tool_result',
               toolUseId: 'agent-1',
-              content: {
-                results: [
-                  {
-                    file: 'git:v0.2.6..v0.2.7',
-                    line: 0,
-                    snippet: 'v0.2.7 tag = a4c92ec7',
-                    context: '版本范围判断：release-notes/v0.2.7.md 明确相比 v0.2.6。',
-                  },
-                  {
-                    file: '/tmp/example/src/lib.rs',
-                    line: 220,
-                    context: '中风险：服务默认监听 0.0.0.0。',
-                  },
-                ],
-              },
+              content: [
+                {
+                  type: 'text',
+                  text: JSON.stringify({
+                    results: [
+                      {
+                        file: 'git:v0.2.6..v0.2.7',
+                        line: 0,
+                        snippet: 'v0.2.7 tag = a4c92ec7',
+                        context: '版本范围判断：release-notes/v0.2.7.md 明确相比 v0.2.6。',
+                      },
+                      {
+                        risk: 'medium',
+                        items: [
+                          {
+                            file: '/tmp/example/src/lib.rs',
+                            line: 220,
+                            context: '中风险：服务默认监听 0.0.0.0。',
+                          },
+                        ],
+                      },
+                    ],
+                  }),
+                },
+              ],
               isError: false,
               timestamp: 2,
             },

desktop/src/components/chat/ToolCallGroup.tsx

@@ -896,17 +896,32 @@ function formatAgentStructuredResult(content: unknown): string {
 
 function parseStructuredAgentContent(content: unknown): Record<string, unknown> | unknown[] | null {
   if (typeof content === 'string') {
-    const trimmed = content.trim()
-    if (!trimmed.startsWith('{') && !trimmed.startsWith('[')) return null
-    try {
-      const parsed = JSON.parse(trimmed) as unknown
-      return typeof parsed === 'object' && parsed !== null ? parsed as Record<string, unknown> | unknown[] : null
-    } catch {
-      return null
-    }
+    return parseStructuredAgentText(content)
   }
 
-  return typeof content === 'object' && content !== null ? content as Record<string, unknown> | unknown[] : null
+  if (Array.isArray(content)) {
+    return parseStructuredAgentText(extractTextContent(content))
+  }
+
+  if (content && typeof content === 'object') {
+    if ('results' in content) return content as Record<string, unknown>
+
+    const extracted = extractTextContent(content)
+    return extracted ? parseStructuredAgentText(extracted) : null
+  }
+
+  return null
+}
+
+function parseStructuredAgentText(text: string): Record<string, unknown> | unknown[] | null {
+  const trimmed = text.trim()
+  if (!trimmed.startsWith('{') && !trimmed.startsWith('[')) return null
+  try {
+    const parsed = JSON.parse(trimmed) as unknown
+    return typeof parsed === 'object' && parsed !== null ? parsed as Record<string, unknown> | unknown[] : null
+  } catch {
+    return null
+  }
 }
 
 function formatAgentStructuredResultItem(result: unknown, index: number): string {
@@ -920,6 +935,29 @@ function formatAgentStructuredResultItem(result: unknown, index: number): string
   const context = getStringField(record, 'context')
   const snippet = getStringField(record, 'snippet')
   const message = getStringField(record, 'message') || getStringField(record, 'text') || getStringField(record, 'summary')
+  const nestedItems = Array.isArray(record.items) ? record.items : []
+
+  if (nestedItems.length > 0) {
+    const label = getStringField(record, 'risk') || getStringField(record, 'title') || message || 'Grouped results'
+    const lines = [`${index + 1}. ${formatAgentGroupLabel(label)}`]
+    if (context) lines.push(`   - ${context}`)
+    if (snippet) lines.push(`   - ${snippet}`)
+
+    nestedItems
+      .map(formatAgentStructuredNestedItem)
+      .filter(Boolean)
+      .forEach((item) => {
+        lines.push(
+          item
+            .split('\n')
+            .map((line, lineIndex) => `${lineIndex === 0 ? '   - ' : '     '}${line}`)
+            .join('\n'),
+        )
+      })
+
+    return lines.join('\n')
+  }
+
   const lines = [`${index + 1}. ${location ? formatInlineCode(location) : 'Result'}`]
 
   if (message) lines.push(`   - ${message}`)
@@ -929,6 +967,31 @@ function formatAgentStructuredResultItem(result: unknown, index: number): string
   return lines.join('\n')
 }
 
+function formatAgentStructuredNestedItem(item: unknown): string {
+  if (!item || typeof item !== 'object' || Array.isArray(item)) {
+    return extractTextContent(item).trim()
+  }
+
+  const record = item as Record<string, unknown>
+  const location = formatAgentResultLocation(record)
+  const context = getStringField(record, 'context')
+  const snippet = getStringField(record, 'snippet')
+  const message = getStringField(record, 'message') || getStringField(record, 'text') || getStringField(record, 'summary')
+  const headingParts = [location ? formatInlineCode(location) : '', message].filter(Boolean)
+  const lines = [headingParts.join(' - ') || 'Result']
+
+  if (context) lines.push(context)
+  if (snippet) lines.push(snippet)
+
+  return lines.join('\n')
+}
+
+function formatAgentGroupLabel(label: string): string {
+  const normalized = label.trim()
+  if (!normalized) return 'Grouped results'
+  return normalized.length > 1 ? `${normalized[0].toUpperCase()}${normalized.slice(1)}` : normalized.toUpperCase()
+}
+
 function formatAgentResultLocation(record: Record<string, unknown>): string {
   const file = getStringField(record, 'file')
   if (!file) return ''