Forward session context to MCP servers

[kashifpk]

Description

Forward session/user context from orchestrator to backend MCP servers for user isolation.

Tasks

• Extract session context from orchestrator requests
• Include context in MCP tool invocations to backends
• Handle context propagation through tool registry
• Support context in both stdio and HTTP transports

Context Flow

Orchestrator → Armory → MCP Server
     │            │           │
     └── context ─┴── context ┘

Acceptance Criteria

• Context flows through to all MCP server backends
• Stateful servers receive user_id for isolation
• Context is optional (stateless servers ignore it)

[kashifpk]

Moved to Post-MVP phase - will implement when stateful MCP servers are added.