[Feature] RPC scope extension: expose orchestration control methods for remote Runtime

[leiyikang-tech]

Summary

The Orca Runtime RPC server currently exposes a runtime scope with only CLI-level methods. This issue extends the RPC scope to include orchestration control methods, enabling a hub Orca instance to dispatch tasks and manage agents on a remote Runtime.

Current State

• OrcaRuntimeRpcServer binds 0.0.0.0:6768 with WebSocket transport
• RPC method scopes: mobile (252 methods), runtime (CLI-level only)
• Current design purpose: desktop → mobile companion, not desktop → desktop
• No orchestration control methods exposed to remote Runtimes

Gap

A hub Orca cannot instruct a remote Runtime to:

• Create a new agent terminal
• Send a prompt to an existing terminal
• List running terminals and their status
• Approve/deny permission requests
• Query worktree state

Proposed Changes

1. New RPC Scope: orchestration

type OrchestrationRpcMethods = {
  // Terminal management
  "orchestration.createTerminal": (opts: CreateTerminalOpts) => Promise<string>
  "orchestration.listTerminals": () => Promise<TerminalInfo[]>
  "orchestration.sendPrompt": (handle: string, prompt: string) => Promise<void>
  "orchestration.closeTerminal": (handle: string) => Promise<void>
  
  // Status & monitoring
  "orchestration.getTerminalStatus": (handle: string) => Promise<AgentStatusState>
  "orchestration.getTerminalPaneKey": (handle: string) => Promise<string>
  
  // Approval
  "orchestration.approvePermission": (requestId: string) => Promise<void>
  "orchestration.denyPermission": (requestId: string) => Promise<void>
  
  // Worktree
  "orchestration.listWorktrees": () => Promise<WorktreeInfo[]>
  "orchestration.probeWorktreeDrift": (worktreeId: string) => Promise<DriftResult>
  
  // Health
  "orchestration.healthCheck": () => Promise<RuntimeHealthReport>
  "orchestration.capabilityReport": () => Promise<RuntimeCapabilityReport>
}

2. Authentication & Authorization

• Orchestration scope requires a separate auth token (not the mobile token)
• Hub and satellite must exchange orchestration tokens during connection handshake
• Rate limiting: max 10 orchestration RPC calls per second per connection

3. Event Streaming

Remote Runtime pushes status change events to hub via RPC notifications:

type OrchestrationNotification = 
  | { type: "terminal.status_changed", handle: string, status: AgentStatusState }
  | { type: "terminal.created", handle: string, title: string }
  | { type: "terminal.closed", handle: string }
  | { type: "permission.requested", requestId: string, handle: string, toolName: string }
  | { type: "health.degraded", runtimeId: string }

Dependencies

• Prerequisite for: Coordinator remote Runtime dispatch
• Related to: Remote Runtime health check

Estimated Effort

1-2 weeks

Related Code

• src/main/relay/ — RPC server implementation
• src/shared/remote-runtime-client.ts — Remote Runtime client
• src/main/runtime/orchestration/coordinator-runtime.ts — CoordinatorRuntime interface