## Summary
- make EnvironmentProvider::snapshot path-free and keep providers
focused on provider-owned remote environments
- let provider snapshots request local inclusion via include_local, with
environments.toml including local and CODEX_EXEC_SERVER_URL excluding
local
- move reserved local environment construction into EnvironmentManager
using ExecServerRuntimePaths
Follow-up to https://github.com/openai/codex/pull/20667
## Testing
- just fmt
- git diff --check
- devbox: bazel build --bes_backend= --bes_results_url=
//codex-rs/exec-server:exec-server
- devbox: bazel test --bes_backend= --bes_results_url=
//codex-rs/exec-server:exec-server-unit-tests
Co-authored-by: Codex <noreply@openai.com>