docs: add changelog entry for ingestion cost-repair gate split

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Author: flanakin

docs-mslearn/toolkit/changelog.md

@@ -38,6 +38,7 @@ The following section lists features and enhancements that are currently in deve
   - Fixed the `ContractedCost` recompute guard to compare with a null-safe tolerance instead of exact float equality, eliminating millions of no-op rewrites that polluted the `x_SourceValues` audit trail while preserving the null-cost backfill and no longer overwriting an existing cost when the unit price is missing ([#2216](https://github.com/microsoft/finops-toolkit/issues/2216)).
   - Fixed the SQL VMs without Azure Hybrid Benefit recommendation query to join on the SQL VM `virtualMachineResourceId` instead of a case-sensitive VM name match that skipped VMs with uppercase names and dropped duplicate names, and made all Azure Resource Graph join kinds explicit so no query relies on the `innerunique` default ([#2225](https://github.com/microsoft/finops-toolkit/pull/2225)).
   - Switched dimension enrichment in the v1_0/v1_2 ingestion transforms (`PricingUnits`, `Regions`, `ResourceTypes`, `Services`) from `join` to the broadcast-optimized `lookup` operator and deduplicated the `Services` mapping per resource type to prevent cost row fan-out ([#2225](https://github.com/microsoft/finops-toolkit/pull/2225)).
+  - Fixed `ListCost`/`ContractedCost` never being repaired for rows without a Microsoft meter or offer ID (for example, third-party Marketplace/ISV purchases), which left `ListCost` at 0 despite a real `EffectiveCost` and corrupted Effective Savings Rate reporting; also cleared the `MissingListCost` data-quality flag once a row is successfully repaired instead of leaving it flagged as broken ([#2214](https://github.com/microsoft/finops-toolkit/issues/2214), [#2235](https://github.com/microsoft/finops-toolkit/issues/2235)).
 
 ### [FinOps workbooks](workbooks/finops-workbooks-overview.md)