refactor(web): secure Pico websocket access behind launcher auth

- stop exposing the raw Pico token to the frontend
- add /api/pico/info for non-secret Pico connection metadata
- proxy /pico/ws through the launcher with same-origin and dashboard auth checks
- inject the upstream Pico websocket protocol server-side
- update frontend chat connection flow and Vite websocket proxy path
- refresh related docs and tests

web/frontend/src/features/chat/controller.ts

@@ -1,7 +1,6 @@
 import { getDefaultStore } from "jotai"
 import { toast } from "sonner"
 
-import { getPicoToken } from "@/api/pico"
 import {
   loadSessionMessages,
   mergeHistoryMessages,
@@ -131,7 +130,6 @@ export async function connectChat() {
   updateChatStore({ connectionState: "connecting" })
 
   try {
-    const { token } = await getPicoToken()
     const sessionId = activeSessionIdRef
 
     if (generation !== connectionGeneration) {
@@ -139,18 +137,10 @@ export async function connectChat() {
       return
     }
 
-    if (!token) {
-      console.error("No pico token available")
-      updateChatStore({ connectionState: "error" })
-      isConnecting = false
-      scheduleReconnect(generation, sessionId)
-      return
-    }
-
     const wsScheme = window.location.protocol === "https:" ? "wss:" : "ws:"
     const wsUrl = `${wsScheme}//${window.location.host}/pico/ws`
     const url = `${wsUrl}?session_id=${encodeURIComponent(sessionId)}`
-    const socket = new WebSocket(url, [`token.${token}`])
+    const socket = new WebSocket(url)
 
     if (generation !== connectionGeneration) {
       isConnecting = false