docs(docs-next): port home, getting started, architecture (phase 2)

[pratyush618]

Phase 2 of the docs migration: port the highest-traffic content from the Zensical site into the new Fumadocs site at docs-next/. Zensical site at docs/ is untouched and still ships unchanged; this PR only fills in stubs in docs-next/content/docs/.

What's ported (12 pages)

Home (1)

• docs/index.md → docs-next/content/docs/index.mdx — short intro paragraph adapted from the Zensical landing, plus the existing 4-card hub

Getting Started (3)

• docs/getting-started/index.md → docs-next/content/docs/getting-started/concepts.mdx (renamed from "Overview" to "Concepts" per the new IA, with a brief mental-model section added)
• docs/getting-started/installation.md → docs-next/content/docs/getting-started/installation.mdx — Material !!! note admonitions rewritten as Fumadocs <Callout type="info">; bumped Python requirement note to 3.10+ and __version__ to 0.12.0
• docs/getting-started/quickstart.md → docs-next/content/docs/getting-started/quickstart.mdx — Material === "Tab Name" blocks rewritten as Fumadocs <Tabs> / <Tab>

Architecture (8)

• All 8 architecture pages ported (overview, job-lifecycle, worker-pool, scheduler, storage, resources, failure-model, serialization)
• 6 Mermaid diagrams converted from triple-backtick mermaid fences to <Mermaid chart={...} /> (see infrastructure section below)
• meta.json ordering set to: overview → job-lifecycle → worker-pool → scheduler → storage → resources → failure-model → serialization

Infrastructure changes

<Mermaid> component — Fumadocs ships callout/card/tabs but not Mermaid, so PR adds a small client component (docs-next/src/components/mermaid.tsx, ~40 lines) that lazy-imports mermaid, picks the dark/default theme from next-themes, and renders the SVG via dangerouslySetInnerHTML. Registered globally in docs-next/src/components/mdx.tsx so MDX pages can use <Mermaid chart="..." /> without per-file imports.

Direct deps added — mermaid and next-themes (the latter was a transitive dep, now direct because the new component imports it).

Conversion rules applied

Material/Zensical	Fumadocs MDX
# Title (h1)	YAML frontmatter title: + description:
!!! note "X" / !!! warning	<Callout title="X" type="info"> / <Callout type="warn">
<div class="grid cards" markdown>	<Cards> / <Card>
=== "Tab"	<Tabs items={[...]}> / <Tab value="...">
```mermaid fence	<Mermaid chart={...} />
[:octicons-arrow-right-24: Text](path)	[Text →](/docs/path)
:material-icon:{ .lg .middle }	dropped (use lucide-react icons in phase 5)
(other-page.md)	(/docs/section/other-page)

Test plan

• pnpm types:check — clean (✓ Types generated successfully)
• pnpm lint — exit 0 (2 warnings on Fumadocs scaffold's !important CSS, intentional)
• pnpm build — 75 static pages generated (was 66 before this PR), no warnings, no errors
• out/llms.txt and out/llms-full.txt regenerated with new content
• Manual smoke once merged: spin up pnpm --dir docs-next dev, click through all 12 ported pages, verify Mermaid diagrams render in both light and dark mode, verify Tabs and Callouts render correctly
• CI: Build Docs (Next) job stays green

Commits

1. feat(docs-next): add mermaid component — adds <Mermaid> (registered globally), pulls in mermaid + next-themes direct deps
2. docs(docs-next): port home + getting started — 4 MDX files
3. docs(docs-next): port architecture section — 8 MDX files + meta.json ordering

What's NOT in here (next phases)

• API reference content + <APIMethod> component (phase 3)
• Long-tail port: guides, examples, comparison, faq, changelog (phase 4)
• Landing page polish + shadcn-style components (phase 5)
• Cutover (phase 7)