docs (talos hvm): add the Storage pages for Talos Hypervisor

[Iheanacho-ai]

What

Adds the Storage section for Talos Hypervisor:

• upload-and-manage-images.mdx: declare a content library on a Talos volume, then upload, verify, list, replace, and delete its files, and pin a virtual machine's image to a digest.
• create-a-storage-pool.mdx: declare a storage pool on a Talos volume, check its status, and change or remove it.

Why

This is part of the Talos Hypervisor docs for TalosCon. It builds on the navigation in #805, and the combined PR at the end will bring all of the Talos Hypervisor PRs to main.

Change

• public/hypervisor/storage/upload-and-manage-images.mdx: new page.
• public/hypervisor/storage/create-a-storage-pool.mdx: new page. It covers declaring, checking, changing, and removing a pool. Talos main does not yet provision virtual machine disks in storage pools, so the page does not describe using a pool from a virtual machine. A TODO comment marks where that content goes once pool-backed disks land.

Testing

• Ran: make style-check-changed. Every YAML block was loaded and validated with Talos's own config loader and validator, including a VirtualMachineConfig disk with a pinned digest.
• Where: local checkout, against siderolabs/talos main at 8fca673 and siderolabs/extensions main at 7d75c4b
• By: an agent (Claude Code), plus a separate agent that fact-checked both pages against the source, citing file:line
• Result: the style check passes and every YAML block validates. The fact-check confirmed the volume kinds, naming rules, upload, list, overwrite, delete, and digest behavior, the status columns, and the pool's change and remove behavior. It found six issues, all corrected: the NFS example linked to the v1.14 External Volumes page, which covers only virtiofs, and now links to the v1.15 ExternalVolumeConfig reference; files are held only by running virtual machines, which can release them in three ways; a VM disk cannot refer to a pool name that contains an underscore; content libraries and storage pools should use separate volumes; a digest mismatch keeps the virtual machine from starting; and the VOLUME column shows the volume ID. The commands have not been run on a host, because there is no Talos v1.15 alpha build yet. The frontmatter check reports the pages as belonging to no known section until docs (talos hvm): add the Talos Hypervisor navigation structure #805 merges. broken-links will flag the links to the Getting Started pages, which are in a separate PR, and the v1.15 reference links until the Talos v1.15 docs are added.
• Filled from outside the page: nothing. All behavior comes from the Talos source.

[github-actions]

📋 Automated documentation review

⚠️ The reviewer did not finish on commit b82f904 (it timed out or errored) — see the workflow run log. This run did not produce a result; any findings from an earlier run on this PR still stand.

[majabojarska]

This wording might be misleading, since the pool is not "moved". It might set an expectation that the contents will be moved as well. Re-pointing, Re-mapping, or re-targeting would describe this operation more accurately.

[Iheanacho-ai]

thank you just made the change!

[majabojarska]

Overall ✔️

[sterlingkoch]

Merged as part of #867.