Add Python app-server SDK (#14435)

## TL;DR
Bring the Python app-server SDK from `main-with-prs-13953-and-14232`
onto current `main` as a standalone SDK-only PR.

- adds the new `sdk/python` and `sdk/python-runtime` package trees
- keeps the scope to the SDK payload only, without the unrelated
branch-history or workflow changes from the source branch
- regenerates `sdk/python/src/codex_app_server/generated/v2_all.py`
against current `main` schema so the extracted SDK matches today's
protocol definitions

## Validation
- `PYTHONPATH=sdk/python/src python3 -m pytest sdk/python/tests`

Co-authored-by: Codex <noreply@openai.com>

sdk/python-runtime/hatch_build.py

@@ -0,0 +1,15 @@
+from __future__ import annotations
+
+from hatchling.builders.hooks.plugin.interface import BuildHookInterface
+
+
+class RuntimeBuildHook(BuildHookInterface):
+    def initialize(self, version: str, build_data: dict[str, object]) -> None:
+        del version
+        if self.target_name == "sdist":
+            raise RuntimeError(
+                "codex-cli-bin is wheel-only; build and publish platform wheels only."
+            )
+
+        build_data["pure_python"] = False
+        build_data["infer_tag"] = True