fix(memory): add CUSTOM block to session.py templates

Without this, selecting CUSTOM as the only strategy would render
an empty retrieval_config dict with no guidance. Now both HTTP and
A2A Strands templates include a CUSTOM Handlebars block with a
TODO comment guiding users to add their own namespace and
retrieval config.

Constraint: CUSTOM is self-managed — no default namespaces to vend
Rejected: Auto-generating a placeholder namespace | would mislead users into thinking it works out of the box
Confidence: high
Scope-risk: narrow

Author: aidandaly24

src/assets/__tests__/__snapshots__/assets.snapshot.test.ts.snap

@@ -1701,6 +1701,11 @@ def get_memory_session_manager(session_id: str, actor_id: str) -> Optional[Agent
 {{/if}}
 {{#if (includes memoryProviders.[0].strategies "SUMMARIZATION")}}
         f"/summaries/{actor_id}/{session_id}": RetrievalConfig(top_k=3, relevance_score=0.5),
+{{/if}}
+{{#if (includes memoryProviders.[0].strategies "CUSTOM")}}
+        # TODO: Add your custom namespace and retrieval config.
+        # Custom strategies use user-controlled extraction logic.
+        # Example: f"/custom/{actor_id}/data": RetrievalConfig(top_k=3, relevance_score=0.5),
 {{/if}}
     }
 {{/if}}
@@ -3986,6 +3991,11 @@ def get_memory_session_manager(session_id: str, actor_id: str) -> Optional[Agent
 {{/if}}
 {{#if (includes memoryProviders.[0].strategies "SUMMARIZATION")}}
         f"/summaries/{actor_id}/{session_id}": RetrievalConfig(top_k=3, relevance_score=0.5),
+{{/if}}
+{{#if (includes memoryProviders.[0].strategies "CUSTOM")}}
+        # TODO: Add your custom namespace and retrieval config.
+        # Custom strategies use user-controlled extraction logic.
+        # Example: f"/custom/{actor_id}/data": RetrievalConfig(top_k=3, relevance_score=0.5),
 {{/if}}
     }
 {{/if}}

src/assets/python/a2a/strands/capabilities/memory/session.py

@@ -21,6 +21,11 @@ def get_memory_session_manager(session_id: str, actor_id: str) -> Optional[Agent
 {{/if}}
 {{#if (includes memoryProviders.[0].strategies "SUMMARIZATION")}}
         f"/summaries/{actor_id}/{session_id}": RetrievalConfig(top_k=3, relevance_score=0.5),
+{{/if}}
+{{#if (includes memoryProviders.[0].strategies "CUSTOM")}}
+        # TODO: Add your custom namespace and retrieval config.
+        # Custom strategies use user-controlled extraction logic.
+        # Example: f"/custom/{actor_id}/data": RetrievalConfig(top_k=3, relevance_score=0.5),
 {{/if}}
     }
 {{/if}}

src/assets/python/http/strands/capabilities/memory/session.py

@@ -21,6 +21,11 @@ def get_memory_session_manager(session_id: str, actor_id: str) -> Optional[Agent
 {{/if}}
 {{#if (includes memoryProviders.[0].strategies "SUMMARIZATION")}}
         f"/summaries/{actor_id}/{session_id}": RetrievalConfig(top_k=3, relevance_score=0.5),
+{{/if}}
+{{#if (includes memoryProviders.[0].strategies "CUSTOM")}}
+        # TODO: Add your custom namespace and retrieval config.
+        # Custom strategies use user-controlled extraction logic.
+        # Example: f"/custom/{actor_id}/data": RetrievalConfig(top_k=3, relevance_score=0.5),
 {{/if}}
     }
 {{/if}}