## Why
Config layer provenance describes how effective configuration was
assembled, so it belongs with the config loader rather than in
app-server's serialized API types.
## What changed
- Moved `ConfigLayerSource`, `ConfigLayerMetadata`, and `ConfigLayer`
ownership into `codex-config`.
- Kept app-server's wire payloads unchanged and added explicit
conversions at the app boundary.
- Removed lower-level app-server-protocol dependencies from config
consumers.
## Stack
This is PR 3 of 6, stacked on [PR
#29721](https://github.com/openai/codex/pull/29721). Review only the
delta from `codex/split-auth-domain-types`. Next: [PR
#29723](https://github.com/openai/codex/pull/29723).
## Validation
- `codex-config` coverage passed.
- App-server config-manager and config RPC coverage passed.
## Summary
PR 3 of 5 in the cloud-managed config client stack.
Adds enterprise-managed cloud config as a first-class config layer
source. The layer metadata is preserved through config loading,
diagnostics, debug output, hook attribution, and app-server protocol
surfaces.
## Details
- Enterprise-managed config becomes a normal config layer source with
backend-supplied `id` and display `name` attached for provenance.
- These layers are designed to behave like non-file managed config: they
can surface syntax/type diagnostics by layer name even though there is
no physical config file.
- Relative path settings are resolved from a stored config base so
cloud-delivered config remains consistent with existing MDM-delivered
config semantics.
- Hook attribution distinguishes config-delivered hooks from
requirements-delivered hooks via `HookSource::CloudManagedConfig`.
- This remains pull-based and snapshot-oriented; the PR adds layer
identity/diagnostics, not dynamic reload behavior.
## Validation
Validated through the targeted stack checks after rebasing onto current
`main`:
- Rust crate tests for
config/hooks/cloud-config/backend-client/app-server-protocol
- Filtered `codex-core` and `codex-app-server` `cloud_config_bundle`
tests
- Python generated-file contract test
- `cargo shear --deny-warnings`
- Targeted `argument-comment-lint` for config/hooks
