[docs-scanner] Contradictory information about default docker driver support for cache backends

[docker-agent]

Files:

• content/manuals/build/cache/backends/_index.md
• content/manuals/build/cache/backends/gha.md
• content/manuals/build/cache/backends/registry.md

Issue

The documentation contradicts itself about whether the default docker driver supports certain cache backends.

In _index.md (lines 18-21):

The default docker driver supports the inline, local, registry, and gha cache backends, but only if you have enabled the containerd image store.

In gha.md (lines 11-13):

This cache storage backend is not supported with the default docker driver. To use this feature, create a new builder using a different driver.

In registry.md (lines 15-17):

This cache storage backend is not supported with the default docker driver. To use this feature, create a new builder using a different driver.

Why this matters

A reader trying to use the GitHub Actions cache or registry cache with the default docker driver will get conflicting information:

• The overview page tells them it IS supported (with containerd enabled)
• The specific backend pages tell them it is NOT supported and they must create a new builder

This directly contradicts the reader's ability to determine whether they need to create a new builder or can use their existing default driver.

Suggested fix

Determine which statement is correct:

Option 1: If the default docker driver DOES support these backends with containerd:

• Remove or update the warning in gha.md and registry.md to match _index.md
• Consider adding a note about requiring containerd image store

Option 2: If the default docker driver does NOT support these backends:

• Update _index.md to remove registry and gha from the list of supported backends
• Keep the warnings in the individual backend pages

Note: local.md and inline.md do not have this warning, which is consistent with _index.md saying they are supported.

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Found by nightly documentation quality scanner