Harden package-manager install policy (#19163)

## Summary

This PR hardens package-manager usage across the repo to reduce
dependency supply-chain risk. It also removes the stale `codex-cli`
Docker path, which was already broken on `main`, instead of keeping a
bitrotted container workflow alive.

## What changed

- Updated pnpm package manager pins and workspace install settings.
- Removed stale `codex-cli` Docker assets instead of trying to keep a
broken local container path alive.
- Added uv settings and lockfiles for the Python SDK packages.
- Updated Python SDK setup docs to use `uv sync`.

## Why

This is primarily a security hardening change. It reduces
package-install and supply-chain risk by ensuring dependency installs go
through pinned package managers, committed lockfiles, release-age
settings, and reviewed build-script controls.

For `codex-cli`, the right follow-up was to remove the local Docker path
rather than keep patching it:

- `codex-cli/Dockerfile` installed `codex.tgz` with `npm install -g`,
which bypassed the repo lockfile and age-gated pnpm settings.
- The local `codex-cli/scripts/build_container.sh` helper was already
broken on `main`: it called `pnpm run build`, but
`codex-cli/package.json` does not define a `build` script.
- The container path itself had bitrotted enough that keeping it would
require extra packaging-specific behavior that was not otherwise needed
by the repo.

## Gaps addressed

- Global npm installs bypassed the repo lockfile in Docker and CLI
reinstall paths, including `codex-cli/Dockerfile` and
`codex-cli/bin/codex.js`.
- CI and Docker pnpm installs used `--frozen-lockfile`, but the repo was
missing stricter pnpm workspace settings for dependency build scripts.
- Python SDK projects had `pyproject.toml` metadata but no committed
`uv.lock` coverage or uv age/index settings in `sdk/python` and
`sdk/python-runtime`.
- The secure devcontainer install path used npm/global install behavior
without a local locked package-manager boundary.
- The local `codex-cli` Docker helper was already broken on `main`, so
this PR removes that stale Docker path instead of preserving a broken
surface.
- pnpm was already pinned, but not to the current repo-wide pnpm version
target.

## Verification

- `pnpm install --frozen-lockfile`
- `.devcontainer/codex-install`: `pnpm install --prod --frozen-lockfile`
- `.devcontainer/codex-install`: `./node_modules/.bin/codex --version`
- `sdk/python`: `uv lock --check`, `uv sync --locked --all-extras
--dry-run`, `uv build`
- `sdk/python-runtime`: `uv lock --check`, `uv sync --locked --dry-run`,
`uv build --wheel`
- `pnpm -r --filter ./sdk/typescript run build`
- `pnpm -r --filter ./sdk/typescript run lint`
- `pnpm -r --filter ./sdk/typescript run test`
- `node --check codex-cli/bin/codex.js`
- `docker build -f .devcontainer/Dockerfile.secure -t codex-secure-test
.`
- `cargo build -p codex-cli`
- repo-wide package-manager audit

.devcontainer/Dockerfile.secure

@@ -4,9 +4,11 @@ ARG TZ
 ARG DEBIAN_FRONTEND=noninteractive
 ARG NODE_MAJOR=22
 ARG RUST_TOOLCHAIN=1.92.0
-ARG CODEX_NPM_VERSION=latest
+# Keep this in sync with .devcontainer/codex-install/package.json and pnpm-lock.yaml.
+ARG CODEX_NPM_VERSION=0.121.0
 
 ENV TZ="$TZ"
+ENV COREPACK_ENABLE_DOWNLOAD_PROMPT=0
 
 SHELL ["/bin/bash", "-o", "pipefail", "-c"]
 
@@ -43,12 +45,18 @@ RUN apt-get update \
     && apt-get clean \
     && rm -rf /var/lib/apt/lists/*
 
+COPY .devcontainer/codex-install/package.json \
+     .devcontainer/codex-install/pnpm-lock.yaml \
+     .devcontainer/codex-install/pnpm-workspace.yaml \
+     /opt/codex-install/
+
 RUN curl -fsSL "https://deb.nodesource.com/setup_${NODE_MAJOR}.x" | bash - \
     && apt-get update \
     && apt-get install -y --no-install-recommends nodejs \
-    && npm install -g corepack@latest "@openai/codex@${CODEX_NPM_VERSION}" \
-    && corepack enable \
-    && corepack prepare pnpm@10.28.2 --activate \
+    && test "$(node -p "require('/opt/codex-install/package.json').dependencies['@openai/codex']")" = "${CODEX_NPM_VERSION}" \
+    && cd /opt/codex-install \
+    && corepack pnpm install --prod --frozen-lockfile \
+    && ln -s /opt/codex-install/node_modules/.bin/codex /usr/local/bin/codex \
     && apt-get clean \
     && rm -rf /var/lib/apt/lists/*