browser relay: multi-session override, stale session recovery, better error feedback

- relay accepts new extension connections by closing old one (last wins, code 4000)
- extension recognizes code 4000 and stops auto-reconnect (shows "replaced" badge)
- fix ping interval race where old WS close handler killed new connection's pings
- retry CDP commands on "Session with given id not found" by re-attaching debugger
- describeError() maps known errors to user-friendly badge tooltips
- persisted relay tokens restored on server start
- user-scoped token salts, token regeneration/deletion endpoints
- extension download endpoint, integrations UI for browser relay setup
- browser relay env vars passed to pi-bridge sandboxes
- browser screen layout with chat panel and prompt prefix

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/databases/officer_db/src/index.ts

@@ -29,6 +29,7 @@ export {
   deleteServerIntegration,
   getUserIntegrations,
   getUserIntegration,
+  getIntegrationsByProvider,
   upsertUserIntegration,
   deleteUserIntegration,
   findUserByIntegrationConfig,

src/databases/officer_db/src/queries/integrations.ts

@@ -38,6 +38,10 @@ export async function getUserIntegrations(userId: number): Promise<UserIntegrati
   return db.select().from(userIntegrations).where(eq(userIntegrations.userId, userId));
 }
 
+export async function getIntegrationsByProvider(provider: string): Promise<UserIntegrationSelect[]> {
+  return db.select().from(userIntegrations).where(eq(userIntegrations.provider, provider));
+}
+
 export async function getUserIntegration(userId: number, provider: string): Promise<UserIntegrationSelect | undefined> {
   const [row] = await db
     .select()