docs: add dhi image docs

[kmendell]

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Greptile Summary

This PR adds documentation for Arcane 1.19.2, focusing on the new non-root container runtime user feature and updated image variant descriptions.

• Introduces a "Container runtime user" section in the environment docs explaining ARCANE_DEFAULT_NONROOT, PUID/PGID, and DOCKER_HOST socket-group behavior; adds a matching entry for ARCANE_DEFAULT_NONROOT in config.json.
• Updates next-images.md to reflect that the next tag now uses a hardened Debian-based runtime (replacing the previous Alpine/distroless description), and documents what next-static/next-distroless are suited for.
• Expands the GPU setup guide's important callout to clarify that official images do not bundle vendor GPU utilities and how each vendor's monitoring path is provided at runtime.

Confidence Score: 3/5

The docs change is largely accurate, but a contradiction between the generated env table (defaultValue: false) and the prose (official images set it to true) will be visible to users and could cause confusion about the actual out-of-the-box behavior.

The ARCANE_DEFAULT_NONROOT entry in config.json carries defaultValue false, so the auto-generated Environment Variables table will show this setting as off by default. Meanwhile, the new prose in environment.md and installation.md tells users that official images have it set to true and that Arcane drops to a non-root user by default. Users reconciling those two signals are likely to be misled about whether they need to set the variable explicitly in their own deployments.

static/config.json and content/configuration/environment.md need to agree on what the effective default is for users of official images.

Prompt To Fix All With AI

Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 1
static/config.json:78-86
**`defaultValue` contradicts documented official-image behavior**

`config.json` records `"defaultValue": "false"` for `ARCANE_DEFAULT_NONROOT`, so the generated `<EnvTable />` on the Environment Variables page will show users that this setting defaults to `false`. However, `environment.md` (added in this same PR) explicitly states "Official Arcane images set `ARCANE_DEFAULT_NONROOT=true`", and `installation.md` says images "drop to a non-root runtime user by default."

A user reading the env table alongside the prose will encounter contradictory signals about what the actual default behavior is. If official images hardcode `ARCANE_DEFAULT_NONROOT=true` in the `Dockerfile` or entrypoint, that distinction should be surfaced — either by noting in the description that the code default differs from the image default, or by adjusting `defaultValue` to reflect the shipped-image default and documenting the code-level fallback separately.

_{Reviews (1): Last reviewed commit: "docs: docs for 1.19.2" | Re-trigger Greptile}

Greptile also left 1 inline comment on this PR.

[kmendell]

• docs: add dhi image docs #407 👈 (View in Graphite)
• main

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[greptile-apps]

defaultValue contradicts documented official-image behavior

config.json records "defaultValue": "false" for ARCANE_DEFAULT_NONROOT, so the generated <EnvTable /> on the Environment Variables page will show users that this setting defaults to false. However, environment.md (added in this same PR) explicitly states "Official Arcane images set ARCANE_DEFAULT_NONROOT=true", and installation.md says images "drop to a non-root runtime user by default."

A user reading the env table alongside the prose will encounter contradictory signals about what the actual default behavior is. If official images hardcode ARCANE_DEFAULT_NONROOT=true in the Dockerfile or entrypoint, that distinction should be surfaced — either by noting in the description that the code default differs from the image default, or by adjusting defaultValue to reflect the shipped-image default and documenting the code-level fallback separately.

Prompt To Fix With AI

This is a comment left during a code review.
Path: static/config.json
Line: 78-86

Comment:
**`defaultValue` contradicts documented official-image behavior**

`config.json` records `"defaultValue": "false"` for `ARCANE_DEFAULT_NONROOT`, so the generated `<EnvTable />` on the Environment Variables page will show users that this setting defaults to `false`. However, `environment.md` (added in this same PR) explicitly states "Official Arcane images set `ARCANE_DEFAULT_NONROOT=true`", and `installation.md` says images "drop to a non-root runtime user by default."

A user reading the env table alongside the prose will encounter contradictory signals about what the actual default behavior is. If official images hardcode `ARCANE_DEFAULT_NONROOT=true` in the `Dockerfile` or entrypoint, that distinction should be surfaced — either by noting in the description that the code default differs from the image default, or by adjusting `defaultValue` to reflect the shipped-image default and documenting the code-level fallback separately.

How can I resolve this? If you propose a fix, please make it concise.