dsh-llm-codex-app-server: Registering Local Codex App Server as a DSH Main Model Provider

`dsh-llm-codex-app-server` is a DeepSeek Harness LLM Provider plugin designed to integrate a locally authenticated Codex App Server into DSH's agent loop. This plugin is compatible with DSH versions `>=0.1.2-alpha.1 <0.2.0` and is an out-of-tree bundle, meaning it does not modify the core repository after installation. Its core capabilities include registering `codex-local` as the primary model Provider, reusing the local `CODEX_HOME` authentication state without storing secrets, and supporting session reuse, cold-start context recovery, tool call mapping, and exposing `harness_skill`. The plugin can integrate Codex