Write the stack section: quick start, overview, ASTRA, comparisons

[EiffL]

Fills in the Lightcone Stack section. It follows the shape of fumadocs.dev's introduction (Quick Start, What is, Comparisons, installation, Guides) and adds a page on ASTRA.

Stacked on #10: the base branch is project-selector, so this diff shows only the new work. Merge #10 first; GitHub then retargets this PR to main.

Pages

Page	Path	Source
Quick Start	/	agent-skills README, lightcone-cli install docs, the lightcone skill
What is the Lightcone Stack	/what-is-lightcone	the Pittsburgh 2026 talk (LightconeResearch/talks)
ASTRA	/astra	the ASTRA page from the closed #3, astra-spec.org
Comparisons	/comparisons	Anthropic's Claude Science announcement and docs (Sep 2026)
Installation	/installation	lightcone-cli docs/user/install.md, agent-skills README, jupyterlab-lightcone README
Guides / Your first analysis	/guides/first-analysis	the Union2.1 supernova tutorial from agent-skills, ported to the full stack

• Quick Start.

  • Prerequisites: uv and git (with an identity), plus Claude Code or Codex.
  • Install steps: the Lightcone CLI at its exact version, then the lightcone plugin, with tabs for Claude Code, Codex and the two desktop apps.
  • A first prompt, then what the agent does next.
  • Lightcone Lab as an optional extra.
  • The prerequisites aren't "uv only". lc refuses to run without git, and needs a git identity before its first run. While the release is a pre-release, the CLI also has to be installed at its exact version (lightcone-cli==0.5.0rc5), because a plain install resolves to the older stable 0.4.2.

• What is the Lightcone Stack.

  • The problem: the gap between what gets produced and what can be verified.
  • Code versus paper, and the three properties (traceable, observable, legible).
  • A diagram of the layers, redrawn with the brand's colours so it works in both schemes, as a small StackLayers MDX component. The talk's version is light-only HTML with status labels and doesn't include MySTRA or Lab.
  • The roles of the researcher and the agent.

• ASTRA.

  • What an analysis records.
  • Decisions, universes and the multiverse, with astra-spec.org's example.
  • Evidence, and how each component uses the spec.
  • The astra command through uvx astra-tools@0.2.18.
  • Links to astra-spec.org for the rest.

• Comparisons.

  • Claude Science gets a feature table, with its strengths stated too.
  • It is framed as complementary, since the stack runs in Claude Code.
  • The page avoids claims such as "no provenance", which its artifact records contradict.
  • Short sections cover workflow managers, notebooks and autonomous research agents.

• Installation.

  • Platforms; uv and git (with an HPC note); git identity.
  • The CLI and why its version is pinned; the plugin (tabs synced with the Quick Start).
  • Optional extras: containers, the report preview, Lightcone Lab.
  • Updating and uninstalling. I checked that uv tool install pkg==<new> replaces an installed version, since uv tool upgrade won't move to a pre-release.

• Your first analysis. The tutorial originally used only the astra plugin and let the agent run the scripts itself. The port:

  • starts from the lightcone plugin and lc init;
  • adds format: to outputs;
  • has lc produce the results into results/<universe>/;
  • turns the covariance choice into a decision with two universes;
  • pins astra-tools@0.2.18;
  • ends with a MySTRA report.

  The figure and numbers come from the original tutorial.

Also

• Images in the static export. images: { unoptimized: true } is added to next.config.mjs. Fumadocs renders local images with next/image, whose default loader goes through /_next/image. A static export can't serve that, so the guide's figure was broken; Next.js lists the default loader among its unsupported static-export features.
• MDX components. Tabs and Steps are registered, as the Fumadocs docs describe.
• Sidebar link removed. The "Related" link to astra-spec.org is gone from the sidebar; the ASTRA page links there instead.

Not verified

The guide has not been run end to end with an agent. The prompts follow the lightcone skill's documented workflow, and the YAML excerpts are marked as what you should see "something like". Running it once and adjusting the excerpts is worth doing before we promote it.

Testing

• npm run types:check and npm run build pass.
• Every external link on the new pages returns 200, including the tutorial's data files.
• Checked in a browser: the Quick Start steps and tabs, the diagram, and the guide's figure.

🤖 Generated with Claude Code

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