docs: document the Deno install path for the CLI - #3569

Found during a DX dogfood walk of the public getting-started docs.

Symptom

docs/getting-started/installation.md lists Deno 2.2 or later as a
supported runtime and offers deno add npm:veryfront for project installs,
but Deno then disappears from the rest of the page:

• New scaffolded project — npm / pnpm / yarn / bun tabs, no deno
  tab (even though create-project.md already documents deno init --npm veryfront).
• Install the CLI — ### npm / ### pnpm / ### yarn / ### bun, no
  ### deno.

So a Deno user following the page literally has no documented way to get a
global veryfront binary. The only Deno CLI-install instruction anywhere in
the workspace pointed at jsr:@veryfront/veryfront, which does not exist:

$ curl -s -o /dev/null -w '%{http_code}' https://jsr.io/@veryfront/veryfront
404
$ deno install -gArf jsr:@veryfront/veryfront
Download https://jsr.io/@veryfront/veryfront/meta.json
error: JSR package not found: @veryfront/veryfront

Root cause

The CLI is published to npm only — deno.json declares the unscoped name
veryfront, so no @veryfront/veryfront JSR package exists or could exist.
The working Deno install path goes through Deno's npm: specifier, and that
one line was simply never added to the installation guide when the Deno tab
was added to the "Blank or existing project" CodeGroup.

Verified against the published 0.1.1228 release, in a sandbox outside the
repo with DENO_INSTALL_ROOT pointed at a scratch directory:

$ deno install -gArf npm:veryfront
+ npm:veryfront 0.1.1228
✅ Successfully installed veryfront
$ veryfront --version
  ● Veryfront CLI v0.1.1228

The caveat in the new subsection is also reproduced, not inferred. deno install -g writes a shim that runs deno run npm:veryfront, and Deno
resolves that bare specifier against the nearest package.json /
node_modules walking up from the current working directory — so the
shim's own pinned version is bypassed inside a project that depends on
veryfront:

$ cd /tmp/sb/empty  && veryfront --version   # ● Veryfront CLI v0.1.1228
$ cd /tmp/sb/pinned && veryfront --version   # ● Veryfront CLI v0.1.1226

(/tmp/sb/pinned pins veryfront@0.1.1226 in package.json; the binary
invoked is the same absolute path in both runs.) Without that note, a Deno
user reasonably concludes the global install silently failed.

Fix

Two additions to docs/getting-started/installation.md:

1. deno init --npm veryfront in the "New scaffolded project" CodeGroup,
   matching the Deno tab already documented in create-project.md.
2. A ### deno subsection with deno install -gArf npm:veryfront and the
   cwd-resolution caveat.

No code changes. The related half of this report — the CLI's own update
banner telling users to run deno install -gArf jsr:@veryfront/veryfront —
was already fixed by #3524 (cli/shared/update-check.ts now points at
https://registry.npmjs.org/veryfront/latest and prints
npm install -g veryfront@latest), which shipped in 0.1.1228. The walker
saw the old banner from a stale 0.1.1019 binary resolved out of a
node_modules tree above its cwd — the same cwd-resolution mechanism
described above.

Regression test

tests/docs/guide-content.test.ts — "gives Deno an install path on every
surface the installation guide offers".

It lives there because that file already owns the installation guide's
runtime-support contract: the adjacent test ("states the supported runtime
floors in the getting-started docs") is what asserts the page's Deno 2.2 or later claim in the first place. Asserting that the claim comes with a usable
install path belongs directly beside the claim itself, and the file is
filesystem-only so it stays cheap. The test also asserts the page never
reintroduces jsr:@veryfront/veryfront.

Confirmed failing before the fix, for the right reason:

guide content contracts ... gives Deno an install path on every surface the installation guide offers => FAILED
  ... to contain: "### deno".
FAILED | 0 passed (21 steps) | 1 failed (1 step)

Green after: deno task docs:validate passes end to end (48 guide-contract
tests, 1226 doc links OK), and the full pre-push suite passed.

Note: docs/getting-started/** is the source of truth — .github/workflows/sync-docs.yml
dispatches to veryfront/veryfront-docs on merge, so the public page picks
this up automatically. No change was made in veryfront-docs.

Summary by CodeRabbit

• Documentation

  • Added Deno installation instructions for creating a scaffolded project and installing the Veryfront CLI.
  • Clarified npm-only publication, Deno’s npm: package resolution, and checking the globally installed CLI version.

• Tests

  • Added documentation checks to verify Deno installation guidance remains complete and avoids referencing an unavailable JSR package.