Fix landing page diagram rendering on iOS Safari dark mode

[Copilot]

The hero diagram on the landing page baked its dark-mode colors into @media (prefers-color-scheme: dark) rules embedded inside SVGs referenced via <img> and data URIs. Safari (iOS and macOS) does not evaluate that media query in this context, so the diagram rendered with the light palette on dark-mode iOS Safari, clashing with the surrounding dark page.

Static fallback diagrams

• Split control-plane-dispatch-fallback.svg and control-plane-dispatch-mobile.svg into separate light and new *-dark.svg variants with the palette baked in (no embedded media query).
• Swap them via <picture> / <source media="(prefers-color-scheme: dark)"> in HierarchyHero.astro, matching the pattern already used in docs/architecture.md.

Lottie animation icons

• The animation's embedded icon assets (sparkle, status dots, report card) in control-plane-dispatch.animation.mjs had the same embedded-media-query pattern, referenced via data URIs.
• Reworked these to accept a prefersDark flag and resolve colors in JS instead of relying on the SVG's own media query.
• HierarchyHero.astro now detects prefers-color-scheme: dark via matchMedia, passes it to the animation builders, and re-initializes the animation when the OS scheme changes.

<picture>
  <source media="(prefers-color-scheme: dark)" srcset={dispatchFallbackDark.src} />
  <img src={dispatchFallback.src} ... class="pipeline-image" />
</picture>

[pelikhan]

@copilot generate screenshots

[Copilot]

@copilot generate screenshots

Built the docs site and captured the hero diagram on an iPhone-sized viewport (393×852, iOS Safari UA) with prefers-color-scheme emulated both ways:

• Dark mode: dark background, light text, purple sparkles, and colored status/report elements all render correctly — no more light-palette bleed-through.
• Light mode: unchanged, matches the original light theme.

Both variants now match the surrounding page theme instead of the diagram staying stuck in the light palette under dark mode.

[mnkiefer]

@copilot Revert changes from 1ea52c4

[Copilot]

@copilot Revert changes from 1ea52c4

Done in 005c07f.

[mnkiefer]

Closing in favor of new PR