feat(codex): share sessions across terminal and web

Use one native app-server for terminal, Web and phone clients while retaining the existing CLI and Runner lifecycle.

Synchronize native queues, permissions, question history and steering state; preserve explicit permission precedence and per-turn usage models. Resume inactive clear commands through Runner and reject independent child cold resumes.

Add shared-runtime regression tests, generated protocol fixtures and lifecycle documentation.

shared/src/apiTypes.ts

@@ -571,6 +571,8 @@ export type RewindConversationResponse = {
 /** CLI → hub RPC result for native fork (before HAPI child binding). */
 export type ForkConversationRpcResult = {
     nativeSessionId: string
+    /** Shared runtimes bind the child themselves; hub must not spawn another engine. */
+    sessionId?: string
     /** When true, hub must spawn with --fork-session (Claude). */
     forkSession?: boolean
 }