feat(docs): flare-dispatch.fractalbox.dev opens on a product page; the docs move under /docs/

[debuggingfuture]

flare-dispatch.fractalbox.dev opens on a product page again: what FlareDispatch is, what it costs against GitHub-hosted runners, and where to start. The documentation lives one click away at /docs/, and every docs link already in circulation still resolves.

Problem & Insight

The docs site took over the root domain, so / showed Starlight's docs front page and the product page had nowhere to live. Starlight owns every route in its content collection but leaves src/pages/ alone, so a standalone Astro page can hold / while Starlight serves the docs from a docs/ subdirectory of the same collection. It stays one build, one Worker, one domain.

Take

• / (src/pages/index.astro): hero, billing timeline and cost card, positioning table, a workflow-step / typed-run code sample, platform capabilities, design principles. Every platform claim matches a run or module at HEAD (pr-review, self-heal-pr, packages/bedrock-sigv4, admission-summary.ts, product-demo, ci-triage-pr).
• Cost card: GitHub's current Linux x64 list prices ($0.006 / $0.012 / $0.022 per minute) against 2 vCPU-active minutes on standard-2 (≈ $0.004), so the 14–52× ratio is computed, not written in by hand.
• /benchmarks/: src/data/benchmarks.ts holds a workload profile per run and prices it at build time through @fractalboxdev/flare-dispatch-core/cost, the engine that meters real executions. A rate change in cost.ts reprices the page on the next build. The committed benchmarks.json and the cost.test.ts check that guarded its hand-copied rate card are gone, since nothing is copied any more. The page labels every figure as modeled, not metered.
• /docs/…: the content symlinks move to src/content/docs/docs/, and the sidebar slugs, /llms.txt and /llms-full.txt follow them. The overview drops the splash template for a normal doc page.
• Redirects: public/_redirects 301s /actions/*, /runs/, /substrate/*, /reference/* and /design/* to /docs/…. Verified under wrangler dev.
• Theme: the landing page reads and writes Starlight's starlight-theme key, so the light/dark choice carries across both halves of the site.

The landing page has its own stylesheet (landing.css) instead of sharing Starlight's, because Starlight's reset and layout would fight the page's grid. The palette tokens match brand.css.

Key actions

• astro build green; pnpm test 2371 passed, all internal links valid; astro check 0 errors; no horizontal scroll at 390 px
• Add profiles for check, worker-deploy, improve-pr, self-heal-pr, triage-issues, triage-prs, org-spec-audit and demo-reel, which are registered but not yet on /benchmarks/

[flaredispatch-fractalboxdev]

⚠️ pr-review could not complete: { "step": "checkout", "cause": Error: CheckoutFailed: { "repo": "fractalboxdev/flare-dispatch", "sha": "b13a7f4b71c4c6b10a3be55fa3e17902613a53cb", "cause": Error: git checkout b13a7f4 exited 128: fatal: reference is not a tree: b13a7f4 }, "summaryMd": undefined }

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