Refresh stale convenience-image config examples (SUPENG-409)

[denislemire]

Description

Update copy-pasted .circleci/config.yml examples so they use current next-gen convenience images and supported Linux VM tags.

This is one increment of a larger docs audit (SUPENG-409). Ubuntu 20.04 machine examples in getting-started, migrate, and the configuration reference are already on 24.04/26.04. This PR covers the remaining pasted tags:

• Hello World / config samples: cimg/node:17.2.0 (EOL) → cimg/node:lts (and lts-browsers where the variant is used)
• Getting started and convenience-images: cimg/base:2021.04 → cimg/base:current
• Convenience images and coverage: cimg/go:1.16 → cimg/go:current
• API and private-image samples: legacy circleci/node Docker images → cimg/node
• Arm VM page: drop the Ubuntu 20.04 tag dump that still called ubuntu-2004:current "recommended for all users"; point at 22.04/24.04/26.04 :current and the configuration reference

Contributor templates and the style-guide sample are updated so new pages do not re-copy the old pins. Versioned Server admin proxy examples that used the same Node 17 snippet are aligned.

Reasons

Readers who paste these samples land on deprecated legacy circleci/ images or brownout-bait tags (Node 17, Ubuntu 20.04, 2021-era cimg/base). That contradicts the convenience-images deprecation notice and the Linux VM Gen2 support policy.

Unchanged in this PR: runner SSH/launch-agent copy, contexts security-group language, ECS/ECR retirement, Insights snapshot badge, and VCS matrix work (separate SUPENG-409 PRs).

Content checks

• Vale run locally on the Arm VM rewrite (no new errors on changed lines)
• View the Vale linter results on the ci/circleci: lint job
• Preview the site from the ci/circleci: build job Artifacts tab (index.html)

Formatting:

• Headings remain sentence case
• Public-repo hygiene: ticket IDs only, no customer data

Test plan

• vale on using-arm.adoc (changed section)
• Confirm cimg/node:lts, cimg/node:lts-browsers, cimg/base:current, and cimg/go:current resolve on Docker Hub / Developer Hub
• Spot-check published paths after merge: Hello World, Convenience Images, Using the Arm VM Execution Environment, Using Docker Authenticated Pulls, API developers guide

[linear-code]

SUPENG-409

[circleci-factory-bot]

FAIL 🔴 author-membership ⚙️ author not in allow-list

denislemire is not in the allow-listed users; allowed: rosieyohannan

PASS 🟢 impact-matches-intent ✨ Docs example tag refresh; impact matches intent

Docs-only change to example image tags across circleci-docs .adoc files; the diff matches the stated intent (replace EOL/legacy tags with cimg/*:current/lts, discourage ubuntu-2004). No code consumes these examples, so cross-repo .circleci configs still using ubuntu-2004:current or cimg/base:2021.04 are unaffected and out of scope. Author may optionally confirm cimg/node:lts, cimg/base:current, cimg/go:current resolve on Developer Hub per the test plan.

SKIP ⚪ 6 skipped check(s)

SKIP ⚪ api-auth-and-design ⚙️ no V3/auth signals in diff

no V3 or auth signals in 22 changed file(s): docs/contributors/modules/docs-style/pages/using-code-samples.adoc, docs/contributors/modules/templates/pages/template-conceptual.adoc, docs/contributors/modules/templates/pages/template-how-to.adoc, docs/contributors/modules/templates/pages/template-tutorial.adoc, docs/guides/modules/execution-managed/pages/circleci-images.adoc, docs/guides/modules/execution-managed/pages/private-images.adoc, docs/guides/modules/execution-managed/pages/using-arm.adoc, docs/guides/modules/getting-started/pages/config-intro.adoc (+14 more)

SKIP ⚪ agents-md-respect ✨ Image-tag refresh respects style-guide rules

The diff swaps stale convenience-image tags in code examples and rewrites the Arm images section; xref link text uses title case, prose is active voice, and no AGENTS.md rule is clearly broken. The new xref targets (configuration-reference anchor and linux-vm-support-policy.adoc) exist per the explored context, so nothing here violates the instruction files.

SKIP ⚪ git-hygiene ⚙️ git history is clean

no merge commits, and no problems with the commit messages

SKIP ⚪ go-best-practices ⚙️ no Go changes to review

no reviewable Go changes among 22 changed file(s)
ignoring 22 non-Go files: docs/contributors/modules/docs-style/pages/using-code-samples.adoc, docs/contributors/modules/templates/pages/template-conceptual.adoc, docs/contributors/modules/templates/pages/template-how-to.adoc, docs/contributors/modules/templates/pages/template-tutorial.adoc, docs/guides/modules/execution-managed/pages/circleci-images.adoc, docs/guides/modules/execution-managed/pages/private-images.adoc, docs/guides/modules/execution-managed/pages/using-arm.adoc, docs/guides/modules/getting-started/pages/config-intro.adoc (+14 more)

SKIP ⚪ reduces-risk ⚙️ non-test files changed

change touches 20 non-test file(s): docs/contributors/modules/docs-style/pages/using-code-samples.adoc, docs/contributors/modules/templates/pages/template-conceptual.adoc, docs/contributors/modules/templates/pages/template-how-to.adoc, docs/contributors/modules/templates/pages/template-tutorial.adoc, docs/guides/modules/execution-managed/pages/circleci-images.adoc, docs/guides/modules/execution-managed/pages/private-images.adoc, docs/guides/modules/execution-managed/pages/using-arm.adoc, docs/guides/modules/getting-started/pages/config-intro.adoc (+12 more)

SKIP ⚪ server-compat ⚙️ no new required config keys

no new env.MustGet calls added in this PR

_{🤖 factory-bot · codeowner mode · reviewed @ 2026-09-18T23:37:02Z · re-request a review to re-run
[bot e93b483] [config 7d1b49f] [target 22e0d22]}