fix: make local knowledge bases ready for daily use

Knowledge selection was shared globally, document readiness overstated usable content, and important import and source-management paths exposed technical details or lacked safe recovery actions. Knowledge scope now persists per conversation, readiness reflects real processing channels, and the workspace guides users from creation and import into cited chat with controlled source actions.

Release note: 知识库现按对话保存使用范围，准确区分可用、处理中和失败文档，并提供更简洁的创建、检索测试、来源打开、删除确认和失败重试流程。

src/main/knowledge/knowledge-database.ts

@@ -846,6 +846,8 @@ export class KnowledgeDatabase {
       sourceCount: number
       documentCount: number
       indexedDocumentCount: number
+      processingDocumentCount: number
+      failedDocumentCount: number
     }
   > {
     const rows = this.requireDatabase()
@@ -855,8 +857,15 @@ export class KnowledgeDatabase {
            COUNT(DISTINCT d.id) AS document_count,
            COUNT(DISTINCT CASE
              WHEN COALESCE(json_extract(d.metadata, '$.status'), 'ready')
-               <> 'failed'
+               = 'ready'
              THEN d.id END) AS indexed_document_count
+           ,COUNT(DISTINCT CASE
+             WHEN json_extract(d.metadata, '$.status')
+               IN ('queued', 'parsing', 'indexing')
+             THEN d.id END) AS processing_document_count
+           ,COUNT(DISTINCT CASE
+             WHEN json_extract(d.metadata, '$.status') = 'failed'
+             THEN d.id END) AS failed_document_count
          FROM knowledge_bases kb
          LEFT JOIN knowledge_sources s ON s.knowledge_base_id = kb.id
          LEFT JOIN documents d ON d.knowledge_base_id = kb.id
@@ -872,6 +881,14 @@ export class KnowledgeDatabase {
           indexedDocumentCount: asNumber(
             row,
             'indexed_document_count'
+          ),
+          processingDocumentCount: asNumber(
+            row,
+            'processing_document_count'
+          ),
+          failedDocumentCount: asNumber(
+            row,
+            'failed_document_count'
           )
         }
       ])