docs: enrich module docs with binary analysis cross-references

src/quota.rs

@@ -1,5 +1,15 @@
 //! Quota monitor — polls the local LS `GetUserStatus` to track
 //! prompt/flow credits and per-model rate limits without touching Google servers.
+//!
+//! The LS's `GetUserStatus` response contains `cascadeModelConfigData` with
+//! per-model `quotaInfo` (remaining fraction, reset time) and plan-level credit
+//! balances (prompt, flow, flex). This data originates from Google's
+//! `PredictionService/RetrieveUserQuota` / `v1internal:retrieveUserQuota` endpoint,
+//! but asking the LS is simpler since it caches this data locally.
+//!
+//! The credit system uses the `google/internal/cloud/code/v1internal/credits`
+//! proto package with `Credits_CreditType` enum. The `CASCADE_ENFORCE_QUOTA`
+//! config key controls whether quotas are actually enforced.
 
 use serde::Serialize;
 use std::sync::Arc;