[codex] Rename Python SDK AppServerConfig to CodexConfig (#24800)

## Why

`AppServerConfig` is exported as part of the ergonomic Python SDK
surface and passed to `Codex(...)` and `AsyncCodex(...)`. That name
exposes the underlying app-server transport at the same layer where
users are configuring the Codex client. `CodexConfig` makes the common
callsite read naturally and names the object it configures.

## What changed

- Renamed the public configuration dataclass from `AppServerConfig` to
`CodexConfig`.
- Updated `Codex`, `AsyncCodex`, and the transport clients to accept
`CodexConfig`.
- Updated binary-resolution messages, package exports, docs, examples,
and related coverage to use the new public name.

## API impact

```python
from openai_codex import Codex, CodexConfig

with Codex(config=CodexConfig(codex_bin="/path/to/codex")) as codex:
    ...
```

Callers should now import and construct `CodexConfig`; `AppServerConfig`
is no longer part of the Python SDK surface.

## Validation

- `uv run --frozen --extra dev ruff check src/openai_codex scripts
examples tests`
- Tests are deferred to online CI for this PR.

sdk/python/docs/api-reference.md

@@ -1,6 +1,6 @@
 # OpenAI Codex SDK — API Reference
 
-Public surface of `openai_codex` for app-server v2.
+Public surface of `openai_codex` for Codex workflows.
 
 This SDK surface is experimental. Turn streams are routed by turn ID so one client can consume multiple active turns concurrently.
 Thread starts default to `ApprovalMode.auto_review`; turn starts accept an optional `approval_mode` override.
@@ -11,6 +11,7 @@ Thread starts default to `ApprovalMode.auto_review`; turn starts accept an optio
 from openai_codex import (
     Codex,
     AsyncCodex,
+    CodexConfig,
     ApprovalMode,
     Sandbox,
     ChatgptLoginHandle,
@@ -47,12 +48,12 @@ from openai_codex.types import (
 
 - Version: `openai_codex.__version__`
 - Requires Python >= 3.10
-- Public app-server value and event types live in `openai_codex.types`
+- Public Codex protocol value and event types live in `openai_codex.types`
 
 ## Codex (sync)
 
 ```python
-Codex(config: AppServerConfig | None = None)
+Codex(config: CodexConfig | None = None)
 ```
 
 Properties/methods:
@@ -82,7 +83,7 @@ with Codex() as codex:
 ## AsyncCodex (async parity)
 
 ```python
-AsyncCodex(config: AppServerConfig | None = None)
+AsyncCodex(config: CodexConfig | None = None)
 ```
 
 Preferred usage:
@@ -201,7 +202,7 @@ Presets:
 - `Sandbox.workspace_write`: the normal default for projects with a recorded trust decision; read files and write inside the workspace and configured writable roots.
 - `Sandbox.full_access`: run without filesystem access restrictions.
 
-When `sandbox=` is omitted, app-server uses its configured default. A sandbox
+When `sandbox=` is omitted, Codex uses its configured default. A sandbox
 passed to `run(...)` or `turn(...)` applies to that turn and subsequent turns.
 
 ## TurnHandle / AsyncTurnHandle
@@ -249,7 +250,7 @@ Use a plain `str` as shorthand for `TextInput(...)` anywhere a turn input is acc
 
 ## Public Types
 
-The SDK wrappers return and accept public app-server models wherever possible:
+The SDK wrappers return and accept public Codex protocol models wherever possible:
 
 ```python
 from openai_codex.types import (