feat(memory): integrate mem0 + IExternalMemoryPort abstraction

[JustAGhosT]

Summary

Integrate managed memory services (mem0 and alternatives) via a new IExternalMemoryPort abstraction. The current IMeshMemoryStore abstraction covers raw storage backends but not higher-level services that provide automatic memory extraction, deduplication, relationship tracking, and cross-session memory graphs.

Problem

8 store backends and 5 vector providers exist, but no integration with managed memory services like mem0. The current IMeshMemoryStore is too low-level for services that handle memory lifecycle (extraction → deduplication → relationship tracking → retrieval).

Architecture

Two-layer integration:

1. IExternalMemoryPort (new, MetacognitiveLayer) — higher-level port for managed memory services
2. Mem0Adapter (new, FoundationLayer) — implements IExternalMemoryPort via mem0 REST API
3. Mem0MemoryStoreAdapter — wraps IExternalMemoryPort to satisfy IMeshMemoryStore for backward compat

New Interface

public interface IExternalMemoryPort
{
    Task<string> AddMemoryAsync(string content, string userId, IDictionary<string, string>? metadata, CancellationToken ct);
    Task<IReadOnlyList<MemorySearchResult>> SearchMemoryAsync(string query, string userId, int limit, CancellationToken ct);
    Task<IReadOnlyList<MemoryEntry>> GetAllMemoriesAsync(string userId, CancellationToken ct);
    Task<MemoryEntry?> GetMemoryAsync(string memoryId, CancellationToken ct);
    Task DeleteMemoryAsync(string memoryId, CancellationToken ct);
    Task<MemoryHistory> GetHistoryAsync(string memoryId, CancellationToken ct);
}

Integration Points

File	Change
src/MetacognitiveLayer/Protocols/Common/Memory/Interfaces.cs	Add IExternalMemoryPort
src/MetacognitiveLayer/Protocols/Common/Memory/MemoryStoreFactory.cs	Add "mem0" to ResolveMemoryStore(), add config props
src/FoundationLayer/Mem0Integration/ (new)	Mem0Adapter, Mem0Client, Mem0Options

Dependencies

• HttpClient via IHttpClientFactory for mem0 REST API
• Circuit breaker via existing AgentCircuitBreakerPolicy
• Feature flag EnableMem0 via IFeatureFlagManager

Acceptance Criteria

• IExternalMemoryPort defined in MetacognitiveLayer
• Mem0Adapter with circuit breaker in FoundationLayer
• MemoryStoreFactory supports StoreType: "mem0"
• Mem0MemoryStoreAdapter wraps port for backward compat
• Unit tests with mocked HTTP
• XML docs, 0 warnings
• Feature flag EnableMem0 gates the integration

Effort Estimate

5–8 days

Enables

• BacklogCrew and CommsCrew (cross-session memory for conversation/issue context)