[codex-http-state] add per-surface HTTP state store

[cooper-oai]

Why

Native Codex surfaces need cookie-like local HTTP state so a remote service can return opaque rotations without storing each user's request state server-side. This PR isolates persistence from transport, authentication, and product policy.

What changed

• Add codex-http-state, a generic store for opaque per-surface values under ~/.codex/state/.
• Store each surface in its own JSON file and replace files atomically.
• Support compare-and-set rotation without a file lock. Concurrent valid writers are last-writer-wins.
• Advance a sibling clear generation before deleting state so a late response from an earlier login epoch cannot restore cleared state.

Review guide

• The crate intentionally knows nothing about integrity headers, ChatGPT hosts, or login flows.
• The important invariants are atomic replacement, generation-aware clear, and well-formed JSON after concurrent writes.
• Later PRs decide when to read, attach, rotate, and clear these values.

Stack

This is PR 1 of 7 in the native HTTP-state stack.

1. #26137: per-surface store (this PR)
2. #26138: app-server bridge
3. #26139: HTTP and WebSocket transport
4. #26140: login, refresh, logout, and remote control
5. #26141: shared model and backend clients
6. #26142: app-owned requests
7. #26143: standalone CLI requests

Validation

• just test -p codex-http-state
• just fix -p codex-http-state
• just bazel-lock-check

[cooper-oai]

@codex review

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: f8a301c3f5

ℹ️ About Codex in GitHub

Your team has set up Codex to 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 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: f8a301c3f5

ℹ️ About Codex in GitHub

Your team has set up Codex to 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 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[cooper-oai]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. 👍

ℹ️ About Codex in GitHub

Your team has set up Codex to 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 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".