[codex] Prepare Python SDK beta documentation and package metadata (#24836)

## Why

The initial public `openai-codex` beta should read and install like a
normal published Python package before a release tag is created. This
follows merged PR #24828, which establishes the independent SDK beta
release plumbing and exact runtime dependency.

## What changed

- Rewrote `sdk/python/README.md` as a compact PyPI-facing beta package
page: published installation, one quickstart, short login examples,
built-in help, and links to deeper guides.
- Updated the getting-started guide, API reference, FAQ, and examples
index to present the published beta consistently without repeating
onboarding in the package landing page or reference page.
- Made `pip install openai-codex` the primary install path while beta
releases are the only published SDK releases, with `--pre` documented
for opting into prereleases after a stable release exists.
- Added curated `help()` / `pydoc` docstrings across the public API and
generated public convenience methods through
`scripts/update_sdk_artifacts.py`.
- Declared the repository `Apache-2.0` license expression and
Documentation URL in package metadata, without introducing a duplicated
SDK-local license file.
- Kept the source distribution focused on installable package material
(`src/openai_codex`, `README.md`, and `pyproject.toml`); the repository
docs and runnable examples remain linked from the PyPI README.
- Built release artifacts in an Alpine container on the Ubuntu runner,
matching Python SDK CI and allowing type generation to install the
published `musllinux` runtime wheel.
- Added `twine check --strict` to the release workflow so malformed PyPI
metadata or rendered README content fails before publishing.
- Added focused SDK assertions for beta metadata, the exact runtime pin,
source distribution contents, and the built-in Python documentation
surface.

## Validation

- Ran `uv run --frozen --extra dev ruff check
scripts/update_sdk_artifacts.py src/openai_codex
tests/test_public_api_signatures.py
tests/test_artifact_workflow_and_binaries.py` before the final
README-only reductions and review-fix follow-ups.
- Built `openai_codex-0.1.0b1-py3-none-any.whl` and
`openai_codex-0.1.0b1.tar.gz` before the final README-only reductions
and review-fix follow-ups.
- Ran `python -m twine check --strict` on both built artifacts before
the final README-only reductions and review-fix follow-ups.
- Verified artifact metadata reports `Apache-2.0` without a duplicated
SDK-local license file.
- Verified `inspect.getdoc(...)` resolves documentation for the package,
`Codex`, `CodexConfig`, and key generated thread methods.
- Rebased the documentation/readiness change onto merged PR #24828
without changing the intended SDK or workflow file contents.
- Final verification is delegated to online CI for this PR.

sdk/python/scripts/update_sdk_artifacts.py

@@ -918,6 +918,7 @@ def _render_codex_block(
         *_approval_mode_start_signature_lines(),
         *_kw_signature_lines(thread_start_fields),
         "    ) -> Thread:",
+        '        """Create a new Codex conversation thread."""',
         _approval_mode_assignment_line("_approval_mode_settings"),
         "        params = ThreadStartParams(",
         *_approval_mode_model_arg_lines(),
@@ -931,6 +932,7 @@ def _render_codex_block(
         "        *,",
         *_kw_signature_lines(thread_list_fields),
         "    ) -> ThreadListResponse:",
+        '        """List saved conversation threads."""',
         "        params = ThreadListParams(",
         *_model_arg_lines(thread_list_fields),
         "        )",
@@ -943,6 +945,7 @@ def _render_codex_block(
         *_approval_mode_override_signature_lines(),
         *_kw_signature_lines(resume_fields),
         "    ) -> Thread:",
+        '        """Resume an existing conversation thread by ID."""',
         _approval_mode_assignment_line("_approval_mode_override_settings"),
         "        params = ThreadResumeParams(",
         "            thread_id=thread_id,",
@@ -959,6 +962,7 @@ def _render_codex_block(
         *_approval_mode_override_signature_lines(),
         *_kw_signature_lines(fork_fields),
         "    ) -> Thread:",
+        '        """Create a new thread from an existing thread."""',
         _approval_mode_assignment_line("_approval_mode_override_settings"),
         "        params = ThreadForkParams(",
         "            thread_id=thread_id,",
@@ -969,9 +973,11 @@ def _render_codex_block(
         "        return Thread(self._client, forked.thread.id)",
         "",
         "    def thread_archive(self, thread_id: str) -> ThreadArchiveResponse:",
+        '        """Archive a stored conversation thread."""',
         "        return self._client.thread_archive(thread_id)",
         "",
         "    def thread_unarchive(self, thread_id: str) -> Thread:",
+        '        """Restore an archived conversation thread."""',
         "        unarchived = self._client.thread_unarchive(thread_id)",
         "        return Thread(self._client, unarchived.thread.id)",
     ]
@@ -991,6 +997,7 @@ def _render_async_codex_block(
         *_approval_mode_start_signature_lines(),
         *_kw_signature_lines(thread_start_fields),
         "    ) -> AsyncThread:",
+        '        """Create a new Codex conversation thread."""',
         "        await self._ensure_initialized()",
         _approval_mode_assignment_line("_approval_mode_settings"),
         "        params = ThreadStartParams(",
@@ -1005,6 +1012,7 @@ def _render_async_codex_block(
         "        *,",
         *_kw_signature_lines(thread_list_fields),
         "    ) -> ThreadListResponse:",
+        '        """List saved conversation threads."""',
         "        await self._ensure_initialized()",
         "        params = ThreadListParams(",
         *_model_arg_lines(thread_list_fields),
@@ -1018,6 +1026,7 @@ def _render_async_codex_block(
         *_approval_mode_override_signature_lines(),
         *_kw_signature_lines(resume_fields),
         "    ) -> AsyncThread:",
+        '        """Resume an existing conversation thread by ID."""',
         "        await self._ensure_initialized()",
         _approval_mode_assignment_line("_approval_mode_override_settings"),
         "        params = ThreadResumeParams(",
@@ -1035,6 +1044,7 @@ def _render_async_codex_block(
         *_approval_mode_override_signature_lines(),
         *_kw_signature_lines(fork_fields),
         "    ) -> AsyncThread:",
+        '        """Create a new thread from an existing thread."""',
         "        await self._ensure_initialized()",
         _approval_mode_assignment_line("_approval_mode_override_settings"),
         "        params = ThreadForkParams(",
@@ -1046,10 +1056,12 @@ def _render_async_codex_block(
         "        return AsyncThread(self, forked.thread.id)",
         "",
         "    async def thread_archive(self, thread_id: str) -> ThreadArchiveResponse:",
+        '        """Archive a stored conversation thread."""',
         "        await self._ensure_initialized()",
         "        return await self._client.thread_archive(thread_id)",
         "",
         "    async def thread_unarchive(self, thread_id: str) -> AsyncThread:",
+        '        """Restore an archived conversation thread."""',
         "        await self._ensure_initialized()",
         "        unarchived = await self._client.thread_unarchive(thread_id)",
         "        return AsyncThread(self, unarchived.thread.id)",
@@ -1068,6 +1080,7 @@ def _render_thread_block(
         *_approval_mode_override_signature_lines(),
         *_kw_signature_lines(turn_fields),
         "    ) -> TurnHandle:",
+        '        """Start a turn and return a handle for streaming or control."""',
         "        wire_input = _to_wire_input(_normalize_run_input(input))",
         _approval_mode_assignment_line("_approval_mode_override_settings"),
         "        params = TurnStartParams(",
@@ -1093,6 +1106,7 @@ def _render_async_thread_block(
         *_approval_mode_override_signature_lines(),
         *_kw_signature_lines(turn_fields),
         "    ) -> AsyncTurnHandle:",
+        '        """Start a turn and return a handle for streaming or control."""',
         "        await self._codex._ensure_initialized()",
         "        wire_input = _to_wire_input(_normalize_run_input(input))",
         _approval_mode_assignment_line("_approval_mode_override_settings"),