fix(distributions): restore missing prompts storage configuration

All distribution run.yaml files were missing the prompts storage store
configuration that was added in commit 98a5047f9 but lost during the
src/ layout migration. Added prompts store config to all 9 distributions:

  prompts:
    namespace: prompts
    backend: kv_default

This fixes the "storage.stores.prompts must be configured" error in
integration tests.

src/llama_stack/distributions/ci-tests/run.yaml

@@ -247,6 +247,9 @@ storage:
     conversations:
       table_name: openai_conversations
       backend: sql_default
+    prompts:
+      namespace: prompts
+      backend: kv_default
 registered_resources:
   models: []
   shields:

src/llama_stack/distributions/dell/run.yaml

@@ -105,6 +105,9 @@ storage:
     conversations:
       table_name: openai_conversations
       backend: sql_default
+    prompts:
+      namespace: prompts
+      backend: kv_default
 registered_resources:
   models:
   - metadata: {}

src/llama_stack/distributions/meta-reference-gpu/run.yaml

@@ -112,6 +112,9 @@ storage:
     conversations:
       table_name: openai_conversations
       backend: sql_default
+    prompts:
+      namespace: prompts
+      backend: kv_default
 registered_resources:
   models:
   - metadata: {}

src/llama_stack/distributions/nvidia/run.yaml

@@ -100,6 +100,9 @@ storage:
     conversations:
       table_name: openai_conversations
       backend: sql_default
+    prompts:
+      namespace: prompts
+      backend: kv_default
 registered_resources:
   models: []
   shields: []

src/llama_stack/distributions/open-benchmark/run.yaml

@@ -142,6 +142,9 @@ storage:
     conversations:
       table_name: openai_conversations
       backend: sql_default
+    prompts:
+      namespace: prompts
+      backend: kv_default
 registered_resources:
   models:
   - metadata: {}

src/llama_stack/distributions/postgres-demo/run.yaml

@@ -87,6 +87,9 @@ storage:
     conversations:
       table_name: openai_conversations
       backend: sql_default
+    prompts:
+      namespace: prompts
+      backend: kv_default
 registered_resources:
   models:
   - metadata: {}

src/llama_stack/distributions/starter-gpu/run.yaml

@@ -250,6 +250,9 @@ storage:
     conversations:
       table_name: openai_conversations
       backend: sql_default
+    prompts:
+      namespace: prompts
+      backend: kv_default
 registered_resources:
   models: []
   shields:

src/llama_stack/distributions/starter/run.yaml

@@ -247,6 +247,9 @@ storage:
     conversations:
       table_name: openai_conversations
       backend: sql_default
+    prompts:
+      namespace: prompts
+      backend: kv_default
 registered_resources:
   models: []
   shields:

src/llama_stack/distributions/watsonx/run.yaml

@@ -115,6 +115,9 @@ storage:
     conversations:
       table_name: openai_conversations
       backend: sql_default
+    prompts:
+      namespace: prompts
+      backend: kv_default
 registered_resources:
   models: []
   shields: []