docs: sync with official Polymarket docs (2026-07-09)

Updates across 25 files:
- api-reference/core: get-user-combo-activity, get-user-combo-positions
- dev-tooling/python
- polymarket-learn/FAQ: wen-token, what-are-prediction-markets, why-do-i-need-crypto
- polymarket-learn/deposits: coinbase, how-to-withdraw, moonpay, usdc-on-eth
- polymarket-learn/get-started: how-to-deposit, how-to-signup, making-your-first-trade, what-is-polymarket
- polymarket-learn/markets: dispute, how-are-markets-clarified, how-are-markets-created, how-are-markets-resolved
- polymarket-learn/trading: holding-rewards, how-are-prices-calculated, limit-orders, liquidity-rewards, market-orders, no-limits
- resources/error-codes

docs/api-reference/core/get-user-combo-activity.md

@@ -71,6 +71,14 @@ paths:
             default: 0
             minimum: 0
             maximum: 10000
+        - in: query
+          name: cursor
+          schema:
+            type: string
+          description: >-
+            Opaque continuation token from a previous response's
+            pagination.next_cursor. When present it supersedes offset (which is
+            ignored). Invalid, tampered, or cross-endpoint tokens return 400.
       responses:
         '200':
           description: Success
@@ -198,7 +206,12 @@ components:
         next_cursor:
           type: string
           nullable: true
-          description: Opaque cursor for the next page; null when has_more is false.
+          description: >-
+            Opaque signed cursor for the next page; null when has_more is false.
+            Pass it back verbatim as ?cursor= on the next request (keep the same
+            sort where the endpoint has one). Never parse or construct it. On
+            cursor-enabled endpoints this makes deep pagination O(page) and
+            stable against concurrent inserts.
     ComboLeg:
       type: object
       properties: