[runtime] forward runtime apis from app server to exec server

[acrognale-oai]

Summary

• Forward runtime install progress and cancellation between app-server and a separately running exec-server, preserving the public lifecycle introduced by the parent PR.
• Keep the install request active while processing progress notifications and cancellation requests, with process-wide singleton install ownership on exec-server.
• Add transport-level coverage for remote progress and cancellation forwarding.

Test Plan

• Formatting and scoped Clippy checks passed for codex-exec-server.
• cargo test -p codex-exec-server passed, including the remote progress-and-cancel transport test.
• An isolated two-process harness launched separate app-server and exec-server instances, observed progress and cancellation across the transport, then completed installation and verified resource publication under the exec-server CODEX_HOME.

Stack

1. #24111 - Introduce runtime/install API
2. #24112 - Add progress and cancellation APIs
3. #24113 - Forward runtime APIs from app-server to exec-server