docs(changelog): set connectionManagement/accessToken sunset to 2026-10-12

Q4 2026 enforcement date (first working day on/after 10 Oct). Still draft
pending team confirmation and the early-July quarterly email cutoff.

PEP-1751

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: Rachel-Codat

blog/260623-deprecation-connection-management-access-token.md

@@ -1,5 +1,5 @@
 ---
-title: "Upcoming YYYY-MM-DD: Deprecation of the connection management access token endpoint"
+title: "Upcoming 2026-10-12: Deprecation of the connection management access token endpoint"
 date: "2026-06-23"
 tags: ["Deprecation"]
 draft: true
@@ -8,16 +8,18 @@ authors: rachelcodat
 
 <!--
 TODO before publishing:
-  1. Agree the sunset date with the team (PEP-1751 acceptance criteria), following the
-     deprecation schedule in the change policy:
-     https://docs.codat.io/introduction/change-policy#deprecation-schedule
-  2. Replace every YYYY-MM-DD placeholder below (title + body) with the agreed date.
-  3. Set `date` to the publication date.
-  4. Remove the `draft: true` line.
+  1. Confirm the 2026-10-12 sunset date with the team (PEP-1751 acceptance criteria).
+     This is the Q4 2026 enforcement date (first working day on/after Sat 10 Oct).
+     The changelog entry MUST be live before the early-July quarterly developer email
+     (practically ~7 July 2026) to make the Q4 window; otherwise the next date is
+     2027-01-11. See https://docs.codat.io/using-the-api/change-policy#deprecation-schedule
+  2. Set `date` to the publication date.
+  3. Remove the `draft: true` line.
+  4. Add a corresponding entry to the deprecations Google Calendar.
   5. Confirm with #team-documentation before publishing.
 -->
 
-On YYYY-MM-DD, Codat will deprecate the `connectionManagement/accessToken` endpoint used to generate company-specific connection management access tokens.
+On 2026-10-12, Codat will deprecate the `connectionManagement/accessToken` endpoint used to generate company-specific connection management access tokens.
 
 <!--truncate-->
 
@@ -41,7 +43,7 @@ The replacement endpoint returns an access token in the same way and requires no
 
 ## Expected impact if no action is taken
 
-After YYYY-MM-DD, calls to the deprecated endpoint will return a `404` error.
+After 2026-10-12, calls to the deprecated endpoint will return a `404` error.
 
 ```json
 {