docs: a documentation site, opening with the prompt that gets someone running

[lex00]

behold had a long README and no site. This adds one at intentius.io/behold, on the same Astro Starlight stack and the same Pages deploy shape as chant's, so the two read as one project.

The landing page leads with an agent prompt

Not a tutorial:

Clone https://github.com/INTENTIUS/behold and get me looking at a live
infrastructure graph in my browser.

I want the version that needs no cloud account and no credentials — the
bundled demo that runs against a local emulator in Docker. Install what it
needs, start it, and tell me the URL.

Then walk me through what I am looking at: what the colours mean, and how to
get a resource to change colour while I watch.

If Docker is not running, say so and show me the source-graph-only version
instead rather than failing.

It says what to achieve and what to do when the environment does not cooperate, and nothing about which commands to type. That is the onboarding test as a first screen: if a competent stranger — or their agent — cannot get to a running graph from what is written down, the documentation is the bug, not their reading. The page says so.

Six pages, drawn from the README rather than invented

page	what it covers
What behold is	the read-only invariant, and why the mixed estate is the point
Run it in five minutes	both demos, and the three things only Kubernetes can show
Open your own project	source graph with nothing set up, then the overlay, then the tier picker
Reading the graph	the colours, the zoom tiers, cross-substrate edges
Acting on it	Sync / Adopt / gates / rollback, and per-substrate auto-sync
Export a snapshot	the static bundle and where to host it

Two things worth calling out because they came from work landed this week rather than from the README:

• What behold is carries the row that explains feat: resource-rollup component status (substrate-neutral) #98 — on Azure and GCP there is no deploy object, so the stack cannot be the status source, because there isn't one.
• Open your own project names the chant ^0.38.0 floor in the tier-picker section, since a caret on a 0.x pins the minor and that is exactly what made every tier render the same graph (The tier lens does not change the graph for a project whose tiers branch on a build parameter #114).

The workflow

Builds on PRs touching docs/, deploys only from main — so a docs change is checked before it is the live site.

Verified

Site builds, 8 pages. Rendered and checked in both light and dark at its real /behold base.

Worth recording: the first render looked completely unstyled, which I nearly reported as a CSS problem. It was served at / while built for /behold, so every stylesheet 404'd. Re-served under the base it ships with, it is correct — but "the styles are broken" and "I served it wrong" look identical in a screenshot.

Pages still needs enabling on the repo (build_type: workflow) for the deploy job to have somewhere to land. Doing that once this merges.