[codex] GUI conversation editing

[jooh]

Summary

• replace separate submit/stop controls with one line-icon action button that switches between send and stop
• add prompt undo/redo navigation with editable in-place user prompts and branch rewrites through replace_from
• preserve stopped partial assistant output as committed conversation context

Validation

• make all-tests passed locally with sandbox escalation for loopback-bound tests
• node --check internal/web/assets/app.js passed
• in-app browser visual smoke was attempted, but local loopback URLs were blocked with net::ERR_BLOCKED_BY_CLIENT

[jooh]

@codex review

Please focus especially on:

• prompt history selection scroll math in internal/web/assets/app.js, including top/bottom sticky threshold alignment and already-visible selections.
• full-bleed .messages scrollbar layout, zero sticky inset, and user/assistant horizontal offsets in internal/web/assets/app.css.
• persistence and branch-rewrite behavior around replace_from, stopped assistant output, and hydrated existing conversations.

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: fc642aeeaf

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".