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/polymarket-learn/trading/market-orders.md

@@ -208,7 +208,7 @@ GTD orders auto-expire at a specified time. Useful for quoting around known even
       .size(dec!(10))
       .side(Side::Buy)
       .order_type(OrderType::GTD)
-      .expiration(Utc::now() + TimeDelta::hours(1))
+      .expiration(Utc::now() + TimeDelta::minutes(1) + TimeDelta::hours(1))
       .build()
       .await?;
   let signed = client.sign(&signer, order).await?;
@@ -217,9 +217,11 @@ GTD orders auto-expire at a specified time. Useful for quoting around known even
 </CodeGroup>
 
 <Note>
-  There is a security threshold of one minute on GTD expiration. To set an
-  effective lifetime of N seconds, use `now + 60 + N`. For example, for a
-  30-second effective lifetime, set the expiration to `now + 60 + 30`.
+  GTD orders expire one minute before their stated expiration as a security
+  threshold. To set an effective lifetime of N seconds, use `now + 60 + N`.
+  In addition, the expiration must be at least three minutes in the future —
+  orders expiring sooner are rejected — so the minimum effective lifetime is
+  about two minutes.
 </Note>
 
 ***