Fix dataset uprating and salary sacrifice default behavior (#1464)

- Fix dataset uprating bug where region values weren't converted to strings for rent indexing
- Change salary sacrifice default behavior to be static (0) instead of fully optimized (1.0)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <noreply@anthropic.com>

Author: nikhilwoodruff

changelog_entry.yaml

@@ -0,0 +1,6 @@
+- bump: patch
+  changes:
+    fixed:
+      - Dataset uprating bug where region values weren't converted to strings for rent indexing
+      - Salary sacrifice default behavior to be static (0) instead of fully optimized (1.0)
+

policyengine_uk/data/economic_assumptions.py

@@ -162,7 +162,7 @@ def uprate_rent(
     elif year < 2025:
         # We have regional growth rates for private rent.
         regional_growth_rate = growth.ons.private_rental_prices(year)[
-            region.values
+            region.values.astype(str)
         ]
         current_year.household["rent"] = np.where(
             is_private_rented,

policyengine_uk/parameters/gov/contrib/behavioral_responses/employee_salary_sacrifice_reduction_rate.yaml

@@ -5,7 +5,7 @@
 # Most employees would optimize their salary sacrifice to avoid NI charges by reducing it to the cap level.
 description: The percentage by which employees reduce their salary sacrifice pension contributions in response to the salary sacrifice pension cap.
 values:
-  2010-01-01: 1.0  # Default: full optimization (employees reduce to cap level)
+  2010-01-01: 0  # Default: full optimization (employees reduce to cap level)
 metadata:
   unit: /1
   label: Employee salary sacrifice reduction rate in response to cap