[template] Store initial option as index in template select (#11523)

tests/integration/fixtures/host_mode_empty_string_options.yaml

@@ -41,6 +41,17 @@ select:
       - ""  # Empty string at the end
     initial_option: "Choice X"
 
+  - platform: template
+    name: "Select Initial Option Test"
+    id: select_initial_option_test
+    optimistic: true
+    options:
+      - "First"
+      - "Second"
+      - "Third"
+      - "Fourth"
+    initial_option: "Third"  # Test non-default initial option
+
 # Add a sensor to ensure we have other entities in the list
 sensor:
   - platform: template

tests/integration/test_host_mode_empty_string_options.py

@@ -36,8 +36,8 @@ async def test_host_mode_empty_string_options(
 
         # Find our select entities
         select_entities = [e for e in entity_info if isinstance(e, SelectInfo)]
-        assert len(select_entities) == 3, (
-            f"Expected 3 select entities, got {len(select_entities)}"
+        assert len(select_entities) == 4, (
+            f"Expected 4 select entities, got {len(select_entities)}"
         )
 
         # Verify each select entity by name and check their options
@@ -71,6 +71,15 @@ async def test_host_mode_empty_string_options(
         assert empty_last.options[2] == "Choice Z"
         assert empty_last.options[3] == ""  # Empty string at end
 
+        # Check "Select Initial Option Test" - verify non-default initial option
+        assert "Select Initial Option Test" in selects_by_name
+        initial_option_test = selects_by_name["Select Initial Option Test"]
+        assert len(initial_option_test.options) == 4
+        assert initial_option_test.options[0] == "First"
+        assert initial_option_test.options[1] == "Second"
+        assert initial_option_test.options[2] == "Third"
+        assert initial_option_test.options[3] == "Fourth"
+
         # If we got here without protobuf decoding errors, the fix is working
         # The bug would have caused "Invalid protobuf message" errors with trailing bytes
 
@@ -78,7 +87,12 @@ async def test_host_mode_empty_string_options(
         # This ensures empty strings work properly in state messages too
         states: dict[int, EntityState] = {}
         states_received_future: asyncio.Future[None] = loop.create_future()
-        expected_select_keys = {empty_first.key, empty_middle.key, empty_last.key}
+        expected_select_keys = {
+            empty_first.key,
+            empty_middle.key,
+            empty_last.key,
+            initial_option_test.key,
+        }
         received_select_keys = set()
 
         def on_state(state: EntityState) -> None:
@@ -109,6 +123,14 @@ async def test_host_mode_empty_string_options(
         assert empty_first.key in states
         assert empty_middle.key in states
         assert empty_last.key in states
+        assert initial_option_test.key in states
+
+        # Verify the initial option is set correctly to "Third" (not the default "First")
+        initial_state = states[initial_option_test.key]
+        assert initial_state.state == "Third", (
+            f"Expected initial state 'Third' but got '{initial_state.state}' - "
+            f"initial_option not correctly applied"
+        )
 
         # The main test is that we got here without protobuf errors
         # The select entities with empty string options were properly encoded