fix: resolve session provider on backend reads

Session history and token usage reads already have a stable app session id.
Passing provider and project hints from the frontend kept those reads coupled
with provider-specific state that the backend can resolve from the session row.

Resolve token usage provider server-side and narrow the session store read API
to session id plus pagination. This keeps provider-specific storage decisions
behind the backend boundary and makes reconnect, pagination, and load-all use
the same session-owned contract.

src/stores/useSessionStore.ts

@@ -454,9 +454,6 @@ export function useSessionStore() {
   const fetchFromServer = useCallback(async (
     sessionId: string,
     opts: {
-      provider?: LLMProvider;
-      projectId?: string;
-      projectPath?: string;
       limit?: number | null;
       offset?: number;
     } = {},
@@ -511,9 +508,6 @@ export function useSessionStore() {
   const fetchMore = useCallback(async (
     sessionId: string,
     opts: {
-      provider?: LLMProvider;
-      projectId?: string;
-      projectPath?: string;
       limit?: number;
     } = {},
   ) => {
@@ -592,11 +586,6 @@ export function useSessionStore() {
    */
   const refreshFromServer = useCallback(async (
     sessionId: string,
-    _opts: {
-      provider?: LLMProvider;
-      projectId?: string;
-      projectPath?: string;
-    } = {},
   ) => {
     const slot = getSlot(sessionId);
     try {