Remove unused includes and fail the build on broken include references

[dvdksn]

What

Cleans up content/includes/ and hardens the include shortcode so this class of issue can't recur silently.

Remove 10 unused include files

These snippets are no longer referenced by any page via the {{%/* include */%}} shortcode (the _index.md cascade sets render: never, so includes are only ever pulled in by that shortcode):

• aci-ecs-eol.md, compose-eol.md, dev-envs-changing.md, dockerfile-labs-channel.md — stale EOL/status callouts
• buildx-v0.10-disclaimer.md, experimental.md, deploy.md, guides-get-docker.md, open-terminal.md — orphaned snippets
• labspace-quickstart.md — empty file

Fix two broken include references

• scout-early-access.md was deleted in 737ad3c ("scout: remove early access callout") but two environment-integration pages (sysdig.md, cli.md) still included it. Removed the dangling lines.
• reference/compose-file/develop.md included compose/develop.md, which doesn't exist; the file is compose/services-develop.md. Repointed the include at the real file. (This is also why services-develop.md looked unused — it was, due to the typo.)

After this, every include file is referenced and every reference resolves.

Fail the build on broken include references

The shortcode previously called readFile directly, which renders nothing when the target is missing rather than failing — exactly how the two stale references above went unnoticed. It now checks fileExists and errorfs with the shortcode position when the target is missing, mirroring the file/files shortcodes.

Testing

Verified against the project's Hugo (0.163.0 extended) in an isolated minimal site:

• Valid include → renders normally, build succeeds.
• Missing target → build fails with ERROR include shortcode: file "includes/<name>" not found: "<file>:<line>:<col>", naming both the missing file and the offending shortcode location.

scripts/lint.sh passes clean on the edited content pages.

🤖 Generated with Claude Code

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[docker-agent]

Assessment: 🟢 APPROVE

This PR is a well-scoped, correct cleanup. All changes are in added lines only and the implementation is sound.

include.html shortcode hardening: The new fileExists + errorf guard mirrors the existing pattern in file.html and files.html. The path includes/foo.md is consistent with the pre-existing readFile "includes/foo.md" call that has worked correctly for the lifetime of the repo (no includes/ directory exists at the project root, confirming Hugo resolves these relative to content/). The PR's claim of tested behavior against Hugo 0.163.0 is consistent with this.

Broken reference fixes: compose/services-develop.md exists at content/includes/compose/services-develop.md ✓. The scout-early-access.md references are fully removed with no remaining references anywhere in the repo ✓.

Removed includes: All 10 deleted files are stale/orphaned snippets — none are pages, so no redirect aliases are needed.

No documentation style issues, no missing redirects, no vendored file edits, no AI-isms in the changed lines.

[docker-agent]

Assessment: 🟡 NEEDS ATTENTION

One logic issue found in the new include.html shortcode. The removed files and fixed include references look clean.

[docker-agent]

[MEDIUM] readFile is called unconditionally — missing file still reaches readFile even after errorf

The new include.html shortcode places {{ readFile $filePath | safeHTML }} outside the if/end block, so it runs unconditionally regardless of whether fileExists returns true or false:

{{ if not (fileExists $filePath) }}
  {{- errorf "include shortcode: file %q not found: %s" $filePath .Position -}}
{{ end }}
{{ readFile $filePath | safeHTML }}   ← always executed

In Hugo, errorf logs the error and marks the build as failed, but does not halt template execution — it returns an empty string and execution continues. This means when a file is missing: (1) errorf fires and marks the build as failed, (2) readFile is still called on the missing path (returns an empty string silently). The build does fail, but the template continues executing unnecessarily.

The conventional safe pattern in Hugo is to gate readFile inside the else branch:

{{ if fileExists $filePath }}
  {{ readFile $filePath | safeHTML }}
{{ else }}
  {{- errorf "include shortcode: file %q not found: %s" $filePath .Position -}}
{{ end }}

This ensures readFile is only called when the file actually exists, matching the stated intent of the PR.