## Why
The TUI still reached through `codex_app_server_client::legacy_core` to
validate exec-policy rules during local startup. The app server already
owns this validation and reports parse failures through `configWarning`,
so the duplicate TUI preflight preserved an unnecessary core dependency
and could inspect the wrong machine when connected to a remote app
server.
## What changed
- Remove the TUI's direct exec-policy startup check.
- Remove the two exec-policy re-exports from `legacy_core`.
- Rely on the app server's existing config-warning flow for malformed
custom rules in both embedded and remote sessions.
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