feat(06-03): add advisor API wrappers (streamChat, fetchConversations, fetchConversation)

- Types: ChatMessage, ConversationSummary, Conversation
- streamChat: POST /api/advisor/chat with ReadableStream SSE parsing
- fetchConversations: GET with 404-tolerant empty array fallback
- fetchConversation: GET by id

web/src/api/advisor.ts

@@ -0,0 +1,117 @@
+// Typed API wrappers for the HWLab advisor endpoints
+
+export interface ChatMessage {
+  id: string
+  role: 'user' | 'assistant' | 'system'
+  content: string
+  created_at: string
+}
+
+export interface ConversationSummary {
+  id: string
+  started_at: string
+  model: string
+  message_count: number
+}
+
+export interface Conversation {
+  id: string
+  started_at: string
+  model: string
+  messages: ChatMessage[]
+}
+
+export async function fetchConversations(): Promise<ConversationSummary[]> {
+  const res = await fetch('/api/advisor/conversations')
+  if (res.status === 404) return []
+  if (!res.ok) {
+    const body = await res.json().catch(() => ({ error: res.statusText }))
+    throw new Error((body as { error?: string }).error ?? `HTTP ${res.status}`)
+  }
+  return res.json() as Promise<ConversationSummary[]>
+}
+
+export async function fetchConversation(id: string): Promise<Conversation> {
+  const res = await fetch(`/api/advisor/conversations/${id}`)
+  if (!res.ok) {
+    const body = await res.json().catch(() => ({ error: res.statusText }))
+    throw new Error((body as { error?: string }).error ?? `HTTP ${res.status}`)
+  }
+  return res.json() as Promise<Conversation>
+}
+
+export async function streamChat(
+  params: { conversationId?: string; message: string; model: string },
+  onToken: (token: string, conversationId: string) => void,
+  onDone: () => void,
+  onError: (err: string) => void,
+): Promise<void> {
+  let res: Response
+  try {
+    res = await fetch('/api/advisor/chat', {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({
+        conversation_id: params.conversationId,
+        message: params.message,
+        model: params.model,
+      }),
+    })
+  } catch (e) {
+    onError((e as Error).message)
+    return
+  }
+
+  if (!res.ok) {
+    const body = await res.json().catch(() => ({ error: res.statusText }))
+    onError((body as { error?: string }).error ?? `HTTP ${res.status}`)
+    return
+  }
+
+  if (!res.body) {
+    onError('No response body from server')
+    return
+  }
+
+  const reader = res.body.getReader()
+  const decoder = new TextDecoder()
+  let buffer = ''
+
+  try {
+    while (true) {
+      const { done, value } = await reader.read()
+      if (done) break
+
+      buffer += decoder.decode(value, { stream: true })
+
+      // Split on double newline (SSE event delimiter)
+      const events = buffer.split('\n\n')
+      // Keep any incomplete trailing fragment in buffer
+      buffer = events.pop() ?? ''
+
+      for (const event of events) {
+        const dataLine = event
+          .split('\n')
+          .find((line) => line.startsWith('data: '))
+        if (!dataLine) continue
+
+        const data = dataLine.slice('data: '.length).trim()
+
+        if (data === '[DONE]') {
+          onDone()
+          return
+        }
+
+        try {
+          const parsed = JSON.parse(data) as { token: string; conversation_id: string }
+          onToken(parsed.token, parsed.conversation_id)
+        } catch {
+          onError(`Failed to parse SSE event: ${data}`)
+          return
+        }
+      }
+    }
+  } catch (e) {
+    onError((e as Error).message)
+  }
+}