feat(docs): add telemetry for page views, referrers and clicks

[Agustin-Delgado]

What this adds

Telemetry for the docs site, in two layers. One script cannot answer both
questions, so there are two.

The counts. src/routes/+layout.ts starts the analytics and the speed
report of the host. They give the views of a page, where a reader came from,
the country, the device and the speed of a page for real readers. These
scripts come from this domain, so a content blocker does not stop them. That
matters here: the readers of these docs are developers, and many of them run
a blocker. A blocker matches the host of a request, and the requests it stops
never arrive, so the loss is silent and it is not measurable.

The clicks. $lib/docs/telemetry loads an analytics client after the page
hydrates, in an idle moment, so it does not take the main thread from the
demos. It records each click with the element behind it, and it gives the heat
maps. hooks.server.ts puts its requests on a path of this domain, for the
same reason as above.

Privacy

The client writes nothing to the device of the reader (persistence: 'memory'),
so the site needs no consent dialog. The cost is that a reader who comes back
tomorrow is a new reader. The first layer carries the counts that need an
identity, so the cost is small. Session recording is off.

The events

Event	Properties	The question it answers
$pageview	route	Which page a reader opens.
search	query, results	What a reader looks for. results: 0 is a gap.
copy	source, detail	Which snippet a reader takes away.
demo_interact	—	The reader tried the demo, and did not only read it.
github_click	—	How many readers go to the repository.
theme_change	to	How many readers use the dark theme.

Each click also arrives by itself, because the client records them without
instructions. The six above are named by hand, because a name makes a chart.

search with results: 0 is the most valuable: the query is the name of a
component that is missing, or of a page that does not use the word the reader
knows.

To turn it on

Two public variables, read at build time: VITE_POSTHOG_KEY and
VITE_POSTHOG_REGION (eu or us, default eu). The region must be the
region of the project, or the vendor answers with an error that the browser
does not show. See docs/src/lib/docs/telemetry/README.md.

Without the key each function does nothing, the client is not in the bundle,
and no event leaves a test or a development page.

Also in this diff

pnpm-workspace.yaml had core-js: set this to true or false, a placeholder.
A new dependency brought core-js in, and the placeholder made
pnpm install --frozen-lockfile exit 1 with ERR_PNPM_IGNORED_BUILDS, which
would have stopped every job of the CI. core-js only prints a funding notice
at install time, so the answer is false.

Verification

• pnpm run lint, pnpm run typecheck (1093 + 4678 files, 0 errors) and
  pnpm run build:docs are green.
• The docs suite passes: 18 files, 72 tests. Seven of them are new, and they
  cover the proxy: the path it answers, the two hosts, the headers of one hop
  that a copied request must not carry, the address of the reader, and a post
  with its body.
• A build with a key puts the client in a chunk of its own, and not in the
  entry. A build with no key leaves it out of the output.

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Project	Deployment	Actions	Updated
human-kit-ui-docs	Ready	Preview	Sep 25, 2026 2:57pm UTC