Format the markdown with prettier in script/fmt and script/fmt-check (closes #100)

script/fmt and script/fmt-check run prettier 3.8.1 on the markdown after
gofmt, with the same yarn helper and arguments as the copies in
sneak/prompts. prettier is pinned in package.json and yarn.lock;
.prettierrc sets four-space tabs and proseWrap always, and
.prettierignore keeps prettier off REPO_POLICIES.md and vendor/. Plain
script/bootstrap now installs Node and Yarn the way the one in
sneak/prompts does, then prettier; with --cgo it does not, as the
Dockerfile stages that pass it format nothing. The HTML templates stay
out: prettier cannot parse a Go template action inside a tag.

Model: opus-5-5

README.md

@@ -94,9 +94,10 @@ Outside Docker, pixa needs libvips (the image has 8.15) and libheif to run, as
 it uses libvips through CGO; building it also needs their development files,
 `pkg-config` and a C compiler. `script/bootstrap --cgo` installs all of these,
 as the `Dockerfile` does where it compiles pixa. Plain `script/bootstrap`, which
-`script/setup` and `script/cibuild` run, installs only git, make and Go: the
-checks compile pixa in Docker, so the host needs none of the C libraries. Docker
-itself must already be installed.
+`script/setup` and `script/cibuild` run, installs git, make and Go, and Node,
+Yarn and the prettier pinned in `yarn.lock` for formatting the markdown, but
+none of the C libraries: the checks compile pixa in Docker. Docker itself must
+already be installed.
 
 ## Running under upaas
 
@@ -568,9 +569,10 @@ standard: normalized scripts in `script/` are the entrypoints for the
 development workflow, and the Makefile targets are thin shims that call
 them. We provide:
 
-- `script/bootstrap` — install git, make and Go and download the Go modules
-  (idempotent); with `--cgo`, also the C compiler and the libvips and libheif
-  libraries that compiling pixa needs
+- `script/bootstrap` — install git, make, Go, Node, Yarn and prettier and
+  download the Go modules (idempotent); with `--cgo`, the C compiler and the
+  libvips and libheif libraries that compiling pixa needs instead of Node, Yarn
+  and prettier
 - `script/setup` — make a fresh clone ready for development
   (bootstrap, then install-precommit)
 - `script/projectname` — output the project name ("pixa")
@@ -578,8 +580,9 @@ them. We provide:
   `Dockerfile`, tagged `pixa-test`
 - `script/lint` — run golangci-lint: build the `lint` phase of the `Dockerfile`,
   tagged `pixa-lint`; the linter never runs on the host
-- `script/fmt` — format all code (writes)
-- `script/fmt-check` — check formatting (read-only), on the host
+- `script/fmt` — format the Go code with gofmt and the markdown with prettier
+  (writes)
+- `script/fmt-check` — check the same formatting (read-only), on the host
 - `script/check` — run test, lint, and fmt-check
 - `script/docker` — build the Docker image tagged via `script/projectname`, with
   the version from `git describe`; the image's build stage depends on the `lint`
@@ -598,7 +601,11 @@ Every `docker build` in these scripts passes `--no-cache`, so the lint and test
 phases run on every build instead of coming from the build cache.
 `script/check`, `script/cibuild`, `script/docker`, `script/lint`, `script/test`,
 `script/setup` and `script/install-precommit` are the standard copies from
-`sneak/prompts`, kept identical to them.
+`sneak/prompts`, kept identical to them. `script/fmt` and `script/fmt-check` are
+the standard copies with pixa's `gofmt` step kept before prettier. prettier
+formats the markdown only: not the HTML templates, as it cannot parse a Go
+template action inside a tag, and not `REPO_POLICIES.md` (see
+`.prettierignore`), a copy of the one in `sneak/prompts`.
 
 ## Load Test