Document credit packs and per-member reset dates

terms-of-service.md

@@ -52,6 +52,9 @@ You agree not to:
 ## 5. Usage limits
 
 - Membership includes a **monthly credit budget** (currently $15 of usage).
+- Members may also purchase **credit packs**: non-expiring credits drawn only
+  after the monthly budget is exhausted. Credits do not expire and carry over
+  from month to month.
 - When your budget is exhausted, requests pause until the next cycle.
 - The pricing and budget model is itself a governance decision — members can change it through Loomio.