docs(changelog): add entry for product-builder tier comment clarification (#8169)

Added CHANGELOG.md entry documenting the worker allocation tier comment
updates from PR #8251 / issue #8169. Clarifies that N_FULL handles PR
fixes via PR-First Priority rule and N_QUARTER covers UAT, bug hunting,
and test infra pools.

ISSUES CLOSED: #8169

CHANGELOG.md

@@ -265,6 +265,12 @@ The format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
 ### Changed
 
+- **`product-builder` Worker Allocation Tier Comments** (#8169): Clarified the
+  `N_FULL` tier comment to explicitly document that PR fixing is handled by
+  `implementation-pool-supervisor` via its PR-First Priority rule. Updated the
+  `N_QUARTER` comment to enumerate the pools it covers (UAT, bug hunting, test
+  infra). Prevents confusion about which supervisor handles PR fix work.
+
 - **Decision Tree Full ULID Display** (#5825): The `agents plan tree` command now
   displays full 26-character ULIDs for all decisions instead of truncating them to
   8 characters. This enables users to copy decision IDs directly from tree output