Fix issue #24010: warn about containerd separate storage path

[dvdksn]

Adds warning about containerd using a separate storage path from the Docker data directory.

Changes:

• Added IMPORTANT callout in "Disk space usage" section explaining that containerd uses separate storage
• Warns users with custom data directories that they need to configure containerd separately
• Links to containerd configuration documentation for data directory setup

This prevents users from unexpectedly filling their root partition when they assumed their custom data directory configuration would apply to containerd.

Fixes #24010

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[docker-agent]

Assessment: 🟡 NEEDS ATTENTION

This PR adds a valuable warning about containerd using a separate storage path from the Docker data directory. The content addresses a real user issue (filling root partitions when custom data directories are configured).

Issues found:

• 1 style guide violation (bold used for emphasis)
• 1 maintainability concern (external link stability)

[dvdksn]

Thank you for the feedback on both the style violation and link stability concern. You're right on both counts.

I've made the following changes:

• Removed the bold emphasis (our style guide reserves bold for UI elements only, not for emphasis)
• Updated the link to point to the stable v2.0.0 release instead of the latest tag, which should provide better long-term stability

The warning now follows our documentation standards while maintaining a reliable reference.

[SuperNinja-4965]

I would also suggest linking to: https://docs.docker.com/engine/daemon/#configure-the-data-directory-location
The linked page does not specify the config file location and contains alot of information alot of users will not necessarily need.

[dvdksn]

Thanks for the suggestion, @SuperNinja-4965. The bullet list below the callout already links to the internal Docker docs page for configuring Docker's data directory. The callout's external link points specifically to the containerd configuration documentation, which covers configuring containerd's own data directory — a separate step from configuring Docker's data directory. The two links serve different purposes.

Generated by Claude Code

[dvdksn]

You're right, @SuperNinja-4965 — the Docker daemon docs page already covers configuring containerd's data directory. Updated the link to point to the internal docs instead.

[dvdksn]

Sorry about that, my robot underling is not behaving this monday