docs: sync Polymarket docs updates 2026-07-13 - add 90 new pages incl. Perps section

docs/perps/changelog.md

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+> ## Documentation Index
+> Fetch the complete documentation index at: https://docs.polymarket.com/llms.txt
+> Use this file to discover all available pages before exploring further.
+
+# Changelog
+
+> Recent changes to the Polymarket Perps API and platform
+
+Notable changes to the Polymarket Perps API.
+
+<Update label="Jun 11, 2026" description="Cancel responses include order IDs">
+  Cancel responses now include `oid` and `coid` fields.
+</Update>
+
+<Update label="Jun 10, 2026" description="Taker delay added for immediately matching orders">
+  Added a 20ms taker delay for orders that immediately match on entry.
+</Update>
+
+<Update label="Jun 9, 2026" description="Reduce-only orders added">
+  Added the reduce-only field to order submission and order updates.
+</Update>
+
+<Update label="Jun 8, 2026" description="Auto-cancel and rate-limit updates">
+  <ul>
+    <li>
+      Added <code>PATCH /v1/trade/auto-cancel</code> to arm or clear a dead
+      man's switch that cancels all open orders at a specified time.
+    </li>
+
+    <li>
+      Added <code>GET /v1/account/auto-cancel</code> to check the current
+      auto-cancel status, trigger count, and daily reset time.
+    </li>
+
+    <li>Auto-cancel is limited to 10 triggers per UTC day per account.</li>
+
+    <li>
+      Added <code>updateLeverage</code> and <code>autoCancel</code> WebSocket
+      post messages.
+    </li>
+
+    <li>
+      <code>portfolio</code> and <code>balances</code> WebSocket channels no
+      longer push updates on every order or fill, only periodically.
+    </li>
+
+    <li>
+      Rate limit error messages now distinguish between{" "}
+      <code>ip\_rate\_limited</code>, <code>action\_rate\_limited</code>, and{" "}
+      <code>message\_rate\_limited</code>.
+    </li>
+  </ul>
+</Update>