Add shared notes with tabbed pages editable by user and AI

Adds a note_pages table backing a tabbed notes panel where the user and
the model can both read and write. Only page titles (plus a short
preview) are injected into the system prompt on every turn; full page
content is kept out of context and fetched on demand via a read_note
tool, with write_note letting the model append to, replace, or create a
page.

Generalizes llm.resolve_web_search into resolve_tool_calls so the
tool-calling loop handles web_search and the new note tools through one
path. The chat stream emits a notes_updated SSE event when the model
edits a note so the frontend panel can refresh; local edits are tracked
as dirty and never clobbered by that refresh.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

frontend/src/api/client.ts

@@ -22,7 +22,7 @@ export interface Source {
 }
 
 export interface SSEChunk {
-  type: 'session_id' | 'chunk' | 'done' | 'error' | 'sources'
+  type: 'session_id' | 'chunk' | 'done' | 'error' | 'sources' | 'notes_updated'
   value?: string | Source[]
 }
 
@@ -257,3 +257,41 @@ export function streamChat(
 
   return () => controller.abort()
 }
+
+export interface NotePage {
+  id: number
+  title: string
+  content: string
+  position: number
+  updated_at: string
+}
+
+export async function fetchNotePages(): Promise<NotePage[]> {
+  const res = await fetch(`${BASE}/api/notes`)
+  return parseJson<NotePage[]>(res, 'ノート取得')
+}
+
+export async function createNotePage(title: string): Promise<NotePage> {
+  const res = await fetch(`${BASE}/api/notes`, {
+    method: 'POST',
+    headers: { 'Content-Type': 'application/json' },
+    body: JSON.stringify({ title }),
+  })
+  return parseJson<NotePage>(res, 'ページ作成')
+}
+
+export async function updateNotePage(
+  pageId: number,
+  patch: { title?: string; content?: string },
+): Promise<NotePage> {
+  const res = await fetch(`${BASE}/api/notes/${pageId}`, {
+    method: 'PATCH',
+    headers: { 'Content-Type': 'application/json' },
+    body: JSON.stringify(patch),
+  })
+  return parseJson<NotePage>(res, 'ページ更新')
+}
+
+export async function deleteNotePage(pageId: number): Promise<void> {
+  await fetch(`${BASE}/api/notes/${pageId}`, { method: 'DELETE' })
+}