feat(frontend): add per-sub-question types and stream state management

Add SubQuestionSources interface for grouped per-sub-question sources. Convert QueryStreamEvent from flat interface to discriminated union with 7 variants including generating_subquestion and completed with sub_question_sources. Add subQuestionSources to QueryStreamState. Update completed event handler to populate subQuestionSources. Make sub_question_sources optional for backward compatibility with old SSE format.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

frontend/src/lib/queries.tsx

@@ -1,7 +1,7 @@
 import React from 'react'
 import { QueryClient, QueryClientProvider, useMutation, useQuery, useQueryClient } from '@tanstack/react-query'
 import { queryDocument, queryDocumentStream, ingestDocument, listDocuments, listChunks, deleteDocument, deleteChunk, listPromptProfiles, getPromptProfile, activatePromptProfile, updatePrompt, updateAllPrompts, resetPrompts, listQueryHistory, getQueryHistoryDetail, deleteQueryHistory, clearQueryHistory, getHistoryStats } from './api'
-import type { QueryRequest, QueryResponse, QueryStreamEvent, SourceMetadata, IngestResponse, DocumentListResponse, ChunkInfo, DeleteResponse, PromptProfileListResponse, PromptSetResponse, PromptUpdateRequest, PromptBatchUpdateRequest, PromptActivateResponse, PromptStatusResponse, QueryHistoryList, QueryHistoryDetail, HistoryStats, HistoryDeleteResponse } from '../types'
+import type { QueryRequest, QueryResponse, QueryStreamEvent, SourceMetadata, SubQuestionSources, IngestResponse, DocumentListResponse, ChunkInfo, DeleteResponse, PromptProfileListResponse, PromptSetResponse, PromptUpdateRequest, PromptBatchUpdateRequest, PromptActivateResponse, PromptStatusResponse, QueryHistoryList, QueryHistoryDetail, HistoryStats, HistoryDeleteResponse } from '../types'
 import { useState, useCallback, useRef } from 'react'
 
 export const queryClient = new QueryClient()
@@ -16,6 +16,7 @@ export interface QueryStreamState {
   extractedQuestions: string[] | null
   answer: string | null
   sources: SourceMetadata[] | null
+  subQuestionSources: SubQuestionSources[] | null
   phase: 'idle' | 'decomposing' | 'retrieving' | 'filtering' | 'generating' | 'completed' | 'error'
   error: Error | null
 }
@@ -25,6 +26,7 @@ export const useQueryDocumentStream = () => {
     extractedQuestions: null,
     answer: null,
     sources: null,
+    subQuestionSources: null,
     phase: 'idle',
     error: null,
   })
@@ -35,6 +37,7 @@ export const useQueryDocumentStream = () => {
       extractedQuestions: null,
       answer: null,
       sources: null,
+      subQuestionSources: null,
       phase: 'decomposing',
       error: null,
     })
@@ -60,11 +63,15 @@ export const useQueryDocumentStream = () => {
           case 'generating':
             setState(prev => ({ ...prev, phase: 'generating' }))
             break
+          case 'generating_subquestion':
+            setState(prev => ({ ...prev, phase: 'generating' }))
+            break
           case 'completed':
             setState(prev => ({
               ...prev,
               answer: event.answer ?? null,
               sources: event.sources ?? null,
+              subQuestionSources: event.sub_question_sources ?? null,
               phase: 'completed',
             }))
             break
@@ -96,6 +103,7 @@ export const useQueryDocumentStream = () => {
       extractedQuestions: null,
       answer: null,
       sources: null,
+      subQuestionSources: null,
       phase: 'idle',
       error: null,
     })

frontend/src/types/index.ts

@@ -7,6 +7,12 @@ export interface SourceMetadata {
   chunk_file_path: string | null
 }
 
+export interface SubQuestionSources {
+  sub_question_index: number
+  sub_question_text: string
+  sources: SourceMetadata[]
+}
+
 export interface QueryRequest {
   question: string
 }
@@ -14,16 +20,18 @@ export interface QueryRequest {
 export interface QueryResponse {
   extracted_questions: string[]
   answer: string
+  sub_question_sources?: SubQuestionSources[]
   sources: SourceMetadata[]
 }
 
-export interface QueryStreamEvent {
+export type QueryStreamEvent =
-  phase: 'decomposed' | 'retrieving' | 'filtering' | 'generating' | 'completed' | 'error'
+  | { phase: 'decomposed'; extracted_questions: string[] }
-  extracted_questions?: string[]
+  | { phase: 'retrieving' }
-  answer?: string
+  | { phase: 'filtering' }
-  sources?: SourceMetadata[]
+  | { phase: 'generating' }
-  message?: string
+  | { phase: 'generating_subquestion'; sub_question_index: number; sub_question_text: string }
-}
+  | { phase: 'completed'; answer: string; sub_question_sources?: SubQuestionSources[]; sources?: SourceMetadata[] }
+  | { phase: 'error'; message: string }
 
 export interface IngestResponse {
   document_id: string