docs: use a portable Omarchy catalog anchor

[f-trycua]

Scope

Refs #3639. Follow-up to #3641.

Use the plain heading Omarchy and Hyprland and its generated
#omarchy-and-hyprland fragment for the Fleet catalog section.

The local docs renderer supports the explicit [#omarchy-hyprland] anchor
syntax, but the public site renders it as heading text and produces a
different heading ID. The catalog table link therefore does not reach the
Omarchy section on the public site. A plain heading keeps both renderers
consistent.

Only the heading and its table link change. No image references, runtime
behavior, SDK defaults, pools, or deployment configuration change.

Validation

• Production docs build: passed (147 static pages).
• Internal docs link check: passed (0 errors).
• Public docs hygiene check: passed.
• Generated HTML contains matching href="#omarchy-and-hyprland" and
  id="omarchy-and-hyprland".
• Local production preview: the section fragment lands on the visible heading.
• git diff --check: passed.

Post-merge verification

• Merged as e686ee9ad32996bdfba9891852cf50a1269693ae; its tree matches the
  tested candidate.
• The automatic docs rollout completed on September 8, 2026 (UTC).
• The public catalog HTML contains matching link and heading fragments.
• Cua Driver browser verification: clicking the Omarchy table row changes the
  URL to #omarchy-and-hyprland and brings the correct heading into view.
• Verified page: https://cua.ai/docs/reference/sandbox-sdk/os-image-catalog#omarchy-and-hyprland