python-sdk: generated type foundation (all v2 schemas) (#13953)

## Summary
Foundation PR only (base for PR #3).

This PR contains the SDK runtime foundation and generated artifacts:

- pinned runtime binary in `sdk/python/bin/` (`codex` or `codex.exe` by
platform)
- single maintenance script:
`sdk/python/scripts/update_sdk_artifacts.py`
- generated protocol/types artifacts under:
  - `sdk/python/src/codex_app_server/generated/protocol_types.py`
  - `sdk/python/src/codex_app_server/generated/schema_types.py`
  - `sdk/python/src/codex_app_server/generated/v2_all/*`
- generation-contract test wiring (`tests/test_contract_generation.py`)

## Release asset behavior
`update_sdk_artifacts.py` now:
- selects latest release by channel (`--channel stable|alpha`)
- resolves the correct asset for current OS/arch
- extracts platform binary (`codex` on macOS/Linux, `codex.exe` on
Windows)
- keeps runtime on single pinned binary source in `sdk/python/bin/`

## Scope boundary
- ✅ PR #2 = binary + generation pipeline + generated types foundation
- ❌ PR #2 does **not** include examples/integration logic polish (that
is PR #3)

## Validation
- Ran: `python scripts/update_sdk_artifacts.py --channel stable`
- Regenerated and committed resulting generated artifacts
- Local tests pass on branch

sdk/python/src/codex_app_server/generated/__init__.py

@@ -0,0 +1 @@
+"""Auto-generated Python types derived from the app-server schemas."""

sdk/python/src/codex_app_server/generated/notification_registry.py

@@ -0,0 +1,102 @@
+# Auto-generated by scripts/update_sdk_artifacts.py
+# DO NOT EDIT MANUALLY.
+
+from __future__ import annotations
+
+from pydantic import BaseModel
+
+from .v2_all import AccountLoginCompletedNotification
+from .v2_all import AccountRateLimitsUpdatedNotification
+from .v2_all import AccountUpdatedNotification
+from .v2_all import AgentMessageDeltaNotification
+from .v2_all import AppListUpdatedNotification
+from .v2_all import CommandExecOutputDeltaNotification
+from .v2_all import CommandExecutionOutputDeltaNotification
+from .v2_all import ConfigWarningNotification
+from .v2_all import ContextCompactedNotification
+from .v2_all import DeprecationNoticeNotification
+from .v2_all import ErrorNotification
+from .v2_all import FileChangeOutputDeltaNotification
+from .v2_all import FuzzyFileSearchSessionCompletedNotification
+from .v2_all import FuzzyFileSearchSessionUpdatedNotification
+from .v2_all import HookCompletedNotification
+from .v2_all import HookStartedNotification
+from .v2_all import ItemCompletedNotification
+from .v2_all import ItemStartedNotification
+from .v2_all import McpServerOauthLoginCompletedNotification
+from .v2_all import McpToolCallProgressNotification
+from .v2_all import ModelReroutedNotification
+from .v2_all import PlanDeltaNotification
+from .v2_all import ReasoningSummaryPartAddedNotification
+from .v2_all import ReasoningSummaryTextDeltaNotification
+from .v2_all import ReasoningTextDeltaNotification
+from .v2_all import ServerRequestResolvedNotification
+from .v2_all import SkillsChangedNotification
+from .v2_all import TerminalInteractionNotification
+from .v2_all import ThreadArchivedNotification
+from .v2_all import ThreadClosedNotification
+from .v2_all import ThreadNameUpdatedNotification
+from .v2_all import ThreadRealtimeClosedNotification
+from .v2_all import ThreadRealtimeErrorNotification
+from .v2_all import ThreadRealtimeItemAddedNotification
+from .v2_all import ThreadRealtimeOutputAudioDeltaNotification
+from .v2_all import ThreadRealtimeStartedNotification
+from .v2_all import ThreadStartedNotification
+from .v2_all import ThreadStatusChangedNotification
+from .v2_all import ThreadTokenUsageUpdatedNotification
+from .v2_all import ThreadUnarchivedNotification
+from .v2_all import TurnCompletedNotification
+from .v2_all import TurnDiffUpdatedNotification
+from .v2_all import TurnPlanUpdatedNotification
+from .v2_all import TurnStartedNotification
+from .v2_all import WindowsSandboxSetupCompletedNotification
+from .v2_all import WindowsWorldWritableWarningNotification
+
+NOTIFICATION_MODELS: dict[str, type[BaseModel]] = {
+    "account/login/completed": AccountLoginCompletedNotification,
+    "account/rateLimits/updated": AccountRateLimitsUpdatedNotification,
+    "account/updated": AccountUpdatedNotification,
+    "app/list/updated": AppListUpdatedNotification,
+    "command/exec/outputDelta": CommandExecOutputDeltaNotification,
+    "configWarning": ConfigWarningNotification,
+    "deprecationNotice": DeprecationNoticeNotification,
+    "error": ErrorNotification,
+    "fuzzyFileSearch/sessionCompleted": FuzzyFileSearchSessionCompletedNotification,
+    "fuzzyFileSearch/sessionUpdated": FuzzyFileSearchSessionUpdatedNotification,
+    "hook/completed": HookCompletedNotification,
+    "hook/started": HookStartedNotification,
+    "item/agentMessage/delta": AgentMessageDeltaNotification,
+    "item/commandExecution/outputDelta": CommandExecutionOutputDeltaNotification,
+    "item/commandExecution/terminalInteraction": TerminalInteractionNotification,
+    "item/completed": ItemCompletedNotification,
+    "item/fileChange/outputDelta": FileChangeOutputDeltaNotification,
+    "item/mcpToolCall/progress": McpToolCallProgressNotification,
+    "item/plan/delta": PlanDeltaNotification,
+    "item/reasoning/summaryPartAdded": ReasoningSummaryPartAddedNotification,
+    "item/reasoning/summaryTextDelta": ReasoningSummaryTextDeltaNotification,
+    "item/reasoning/textDelta": ReasoningTextDeltaNotification,
+    "item/started": ItemStartedNotification,
+    "mcpServer/oauthLogin/completed": McpServerOauthLoginCompletedNotification,
+    "model/rerouted": ModelReroutedNotification,
+    "serverRequest/resolved": ServerRequestResolvedNotification,
+    "skills/changed": SkillsChangedNotification,
+    "thread/archived": ThreadArchivedNotification,
+    "thread/closed": ThreadClosedNotification,
+    "thread/compacted": ContextCompactedNotification,
+    "thread/name/updated": ThreadNameUpdatedNotification,
+    "thread/realtime/closed": ThreadRealtimeClosedNotification,
+    "thread/realtime/error": ThreadRealtimeErrorNotification,
+    "thread/realtime/itemAdded": ThreadRealtimeItemAddedNotification,
+    "thread/realtime/outputAudio/delta": ThreadRealtimeOutputAudioDeltaNotification,
+    "thread/realtime/started": ThreadRealtimeStartedNotification,
+    "thread/started": ThreadStartedNotification,
+    "thread/status/changed": ThreadStatusChangedNotification,
+    "thread/tokenUsage/updated": ThreadTokenUsageUpdatedNotification,
+    "thread/unarchived": ThreadUnarchivedNotification,
+    "turn/completed": TurnCompletedNotification,
+    "turn/diff/updated": TurnDiffUpdatedNotification,
+    "turn/plan/updated": TurnPlanUpdatedNotification,
+    "turn/started": TurnStartedNotification,
+    "windows/worldWritableWarning": WindowsWorldWritableWarningNotification,
+    "windowsSandbox/setupCompleted": WindowsSandboxSetupCompletedNotification,
+}

sdk/python/src/codex_app_server/generated/v2_types.py

@@ -0,0 +1,25 @@
+"""Stable aliases over full v2 autogenerated models (datamodel-code-generator)."""
+
+from .v2_all.ModelListResponse import ModelListResponse
+from .v2_all.ThreadCompactStartResponse import ThreadCompactStartResponse
+from .v2_all.ThreadListResponse import ThreadListResponse
+from .v2_all.ThreadReadResponse import ThreadReadResponse
+from .v2_all.ThreadTokenUsageUpdatedNotification import (
+    ThreadTokenUsageUpdatedNotification,
+)
+from .v2_all.TurnCompletedNotification import ThreadItem153 as ThreadItem
+from .v2_all.TurnCompletedNotification import (
+    TurnCompletedNotification as TurnCompletedNotificationPayload,
+)
+from .v2_all.TurnSteerResponse import TurnSteerResponse
+
+__all__ = [
+    "ModelListResponse",
+    "ThreadCompactStartResponse",
+    "ThreadListResponse",
+    "ThreadReadResponse",
+    "ThreadTokenUsageUpdatedNotification",
+    "TurnCompletedNotificationPayload",
+    "TurnSteerResponse",
+    "ThreadItem",
+]