Check the SDK's own code before it merges (hq ADR 0237)

A merge-check.sh, the repository's layer of the mesh's merge check (mesh/repo-check), in
the TypeScript toolchain: install from the lock file, type-check, run the suite. The Go,
Python, Rust and C bindings are said as not tested there, never passed silently.

merge-check.sh

@@ -0,0 +1,25 @@
+#!/bin/sh
+# mesh-check-toolchain: typescript
+#
+# The SDK's own check (novox/hq ADR 0237 as amended): the second layer of a pull request's merge check,
+# `mesh/repo-check`, run by the build seat in the mesh's TypeScript toolchain — and by hand.
+#
+# The gate is the build seat's first layer (`mesh/merge-gate`), run because the mesh's module graph builds
+# mesh-sdk from here — and every module whose build packages it. This is the SDK's own: the TypeScript
+# spine every module imports, type-checked and its suite run, its dependencies installed from the lock
+# file alone (public packages: the SDK depends on nothing of the mesh's).
+#
+# **Said, never passed silently**: the Go, Python, Rust and C bindings are not tested in this toolchain.
+# The Go binding's tests run when a Go compiler is present (a person's run), and are said as not run when not.
+set -eu
+
+npm ci --no-audit --no-fund --loglevel=error
+node node_modules/typescript/bin/tsc --noEmit
+npm test
+
+if command -v go >/dev/null 2>&1; then
+	(cd go && test -z "$(gofmt -l .)" && go vet ./... && go test -count=1 ./...)
+else
+	echo "NOT TESTED HERE: go/ (the Go binding) — the TypeScript toolchain holds no Go compiler"
+fi
+echo "NOT TESTED HERE: python/, rust/, c/ — no toolchain of theirs runs a merge check"