MCP-1A: Extract a shared runtime factory and remove global config mutation

[Atharva-Kanherkar]

MCP-1A: Extract a shared runtime factory and remove global config mutation

Summary

Extract a shared runtime/container module used by both FastAPI and MCP, and remove the current thread-unsafe pattern that mutates config.CHROMA_DB_PATH during runtime construction.

Problem

The runtime composition is currently trapped inside MemoryAPIService in api/app.py, which makes it hard to reuse from MCP. It also mutates module-level config state during initialization, which is unsafe under concurrent runtime creation.

Scope

• extract a shared runtime/container module
• make FastAPI consume that runtime instead of owning the wiring
• inject chroma_path directly into store/client construction
• inject embedding dimensions through runtime construction
• move EventRecorder into the shared runtime if it remains common

Acceptance Criteria

• FastAPI and MCP use the same runtime factory
• runtime construction never mutates module-level config to swap Chroma paths
• concurrent runtime creation cannot observe another runtime's database path
• embedding dimensions can be supplied at runtime, enabling future 768→1536 parallel migration into a fresh Chroma path

Dependencies

• Parent: MCP-1: Add an MCP server layer for agentic-memory #55
• Blocks: MCP-1B: Harden core retrieval, contradiction status, and forgetting concurrency #59, MCP-1D: Implement the FastMCP server and transport startup #61, MCP-1E: Add multimodal MCP input handling for local paths and inline payloads #62