[BUG] custom viewer ignored in npm help

Is there an existing issue for this?

• I have searched the existing issues

This issue exists in the latest npm version

• I am using the latest npm

This is not just a request to bump a dependency for a CVE

• This is not solely a request to bump a dependency for a CVE

Current Behavior

Config viewer is completely ignored, unless it's "browser" or "woman":

https://github.com/npm/cli/blob/278df04d3f25d391af3213a243bb9f89e1d11899/lib/commands/help.js#L90

Expected Behavior

According to the docs, viewer should be "the program to use to view help content".

https://github.com/npm/cli/blob/278df04d3f25d391af3213a243bb9f89e1d11899/workspaces/config/lib/definitions/definitions.js#L2750-L2761

Steps To Reproduce

1. npm config --global set viewer batman
2. npm help exec
3. batman is never invoked

Environment

• npm: 12.0.1
• Node.js: v26.5.1
• OS Name: Arch Linux
• System Model Name: x86_64
• npm config:

; "user" config from /home/marmis/.config/npm/npmrc

; cache = "/home/marmis/.cache/npm" ; overridden by env
ignore-scripts = true
; init-module = "/home/marmis/.config/npm/npm-init.js" ; overridden by env
logs-dir = "/home/marmis/.local/state/npm/logs"
min-release-age = 7
viewer = "batman"

; "env" config from environment

cache = "/home/marmis/.cache/npm"
init-module = "/home/marmis/.config/npm/npm-init.js"
userconfig = "/home/marmis/.config/npm/npmrc"

; node bin location = /usr/bin/node
; node version = v26.5.1
; npm local prefix = /home/marmis
; npm version = 12.0.1
; cwd = /home/marmis
; HOME = /home/marmis
; Run `npm config ls -l` to show all defaults.

Start in lib/commands/help.js at the linked handling around line 90, then compare it with the viewer definition in workspaces/config/lib/definitions/definitions.js. Reproduce with npm config --global set viewer batman and npm help exec; done means the configured custom viewer is invoked rather than ignored.