#736 docs: add Hypervel 0.3 notice and port queue serialization docs fix

Adds a notice to the top of the home page and every docs page:

This site is for Hypervel 0.3. Hypervel 0.4 is a ground-up rewrite — launching soon, along with a new website and docs!

It uses the site's existing warning box style. Docs pages get it through the default theme's page-content-top layout slot. The home layout has no slots, so a small wrapper around VPHomeHero adds it there.

Also ports hypervel/hypervel.org#7 (model serialization in queues.md), which was merged after the docs moved into this repo and never made it across.

[!NOTE]

Add Hypervel 0.3 version notice to docs site and fix queue serialization docs

• Adds a VersionNotice warning that the site documents Hypervel 0.3 and that 0.4 is a ground-up rewrite with new docs planned. It appears via a custom Layout.vue and an aliased HomeHero.vue registered in config.js and client.js.
• Reworks queues.md to describe full-model snapshot serialization as the default, with identifier-based serialization via QueueableEntity as an option. Adds an example model implementation, withoutRelations guidance, and updated missing-model notes.
• Behavioral Change: home page and all doc pages now render the version notice; queue docs now state the default serialization behavior differently.

^{Macroscope summarized 8dd3bad.}