Update DP APIs to support namespace re-design

[nborges-aws]

Summary:

Adds support for the new namespacePath field introduced on the memory data-plane APIs (ListMemoryRecords and RetrieveMemoryRecords). This lets callers opt into hierarchical path-prefix retrieval, separate from the existing namespace field (which is evolving toward exact-match semantics service-side).

Description of changes:

New utility (src/bedrock_agentcore/_utils/namespace.py):

• build_namespace_params(namespace, namespace_path) — validates caller input (mutual exclusivity, presence, no wildcards) and produces the correct wire kwargs for boto.

MemoryClient (memory/client.py):

• retrieve_memories() — accepts both namespace and namespace_path. On invalid input (both provided, neither provided, wildcard present), logs an error and returns [] — preserves the existing soft-fail contract of this method.
• process_turn_with_llm() — adds retrieval_namespace_path parameter, forwards to retrieve_memories.

MemorySessionManager (memory/session.py):

• search_long_term_memories() and list_long_term_memory_records() now route the existing namespace_prefix argument to namespacePath. The parameter name and user-facing semantics remain unchanged; only the underlying field is updated.

Strands integration (memory/integrations/strands/session_manager.py):

• _load_ltm() now calls retrieve_memories(namespace_path=...) to preserve the historical hierarchical-scoping behavior under the new API semantics.

Behavior changes for users

• Existing callers using retrieve_memories(namespace=...) continue to work. Namespace will eventually become the exact-match field
• Existing callers using search_long_term_memories(namespace_prefix=...) continue to work as before
• New callers can opt into hierarchical retrieval explicitly via retrieve_memories(namespace_path=...).

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[github-actions]

✅ No Breaking Changes Detected

No public API breaking changes found in this PR.