Add entity memory authority view and benchmark coverage

[yvette-carlisle]

Summary

• Add an entity-scoped memory authority view that joins graph-linked archival notes with attached core memory blocks under read_profile/shared-grant access control.
• Expose the view through GET /v2/entity-memory and MCP tool elf_entity_memory_get.
• Add benchmark coverage tying ELF memory_evolution/core_archival strengths to Mem0/OpenMemory and Letta comparison gates.
• Register the new elf.entity_memory_view/v1 schema in docs.

Validation

• cargo test -p elf-service entity_memory -- --nocapture
• cargo test -p elf-eval --test real_world_job_benchmark memory_authority -- --nocapture
• cargo test -p elf-api openapi_json_route_serves_generated_contract -- --nocapture
• cargo test -p elf-mcp registers_all_tools -- --nocapture
• cargo make lint-fix
• cargo make check
• cargo +nightly fmt --all -- --check
• git diff --check

Authority: XY-1018