Load platform MITM CA roots

[winston-openai]

Why

The managed MITM baseline must come from platform trust, not inherited startup CA overrides that may be command-specific or unreadable inside a sandbox.

What

• load platform-native roots without consulting inherited SSL_CERT_FILE or SSL_CERT_DIR
• keep startup CA overrides out of the baseline managed bundle until child policy can be checked
• cover the startup-override regression in codex-network-proxy

Stack

• This is the first PR.
• Child: Track startup MITM CA env #26314

Validation

• just test -p codex-network-proxy
• just bazel-lock-check

[chatgpt-codex-connector]

💡 Codex Review

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[winston-openai]

@codex review

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 5891f041b2

ℹ️ About Codex in GitHub

Codex has been enabled to automatically review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

When you sign up for Codex through ChatGPT, Codex can also answer questions or update the PR, like "@codex address that feedback".

[winston-openai]

Closing as superseded by the focused #29013 and #29014 stack. The replacement isolates the persisted MITM private key and preserves file-backed custom CAs present at Codex startup, with zero codex-core changes. Per-command bundle materialization, generic sandbox carvebacks, and additional shell-snapshot plumbing are intentionally deferred because they are not required for this scoped completion work.