Background

This was prompted by #26858, where the attached doctor report did not include the editor selection and I had to ask which editor was in use before investigating the external-editor newline issue. Capturing these variables in doctor makes that context available up front in future reports.

codex doctor is intended to capture enough local context to diagnose startup and terminal behavior, but it did not report the environment variables that select an external editor or configure command pagers.

The TUI prefers VISUAL over EDITOR, so missing or unexpected values can explain why the external-editor shortcut fails or launches the wrong command. Pager values are also useful inherited-shell context even though unified exec normalizes its effective pager variables to cat.

These variables can contain arbitrary command arguments or inline environment assignments. The human report is local, but codex doctor --json may be attached to feedback, so the machine-readable report should not include their raw contents.

What Changed

• Report VISUAL and EDITOR in the system environment details, using not set when either variable is absent.
• Report inherited PAGER, GIT_PAGER, GH_PAGER, and LESS values when present.
• Preserve full values in local human output while reducing these fields to set or not set in redacted JSON output.
• Add structured check, JSON-redaction, rendered-output, and snapshot coverage.

How to Test

1. From codex-rs, run Codex with explicit editor and pager variables:

   env VISUAL='code --wait' EDITOR=vim PAGER='less -R' GIT_PAGER=delta GH_PAGER=less LESS=-FRX \
     cargo run -p codex-cli --bin codex -- doctor --no-color

2. Confirm the system details show the full values for all six variables.

3. Unset the pager variables and rerun the command. Confirm pager rows are omitted while missing editor variables are shown as not set.

4. Run the same configured environment with doctor --json. Confirm each configured editor or pager field is reported as set and none of the raw commands or arguments appear in the JSON.

Targeted tests:

• just test -p codex-cli (279 tests passed)