feat: build module UI into its declared browser artifact

ADR 0022 defined what a module UI is and selected React and TypeScript
as the authoring model, but closed by recording that it was not buildable
end to end: `browser.json` preserves JSX, bundler plugins are denied, and
nothing turned a module's `.tsx` into the artifact its manifest declares.
This closes exactly that gap.

esbuild produces the artifact. It was already the right answer before it
was chosen: this workspace resolves esbuild 0.28.1 through Vite/Vitest
today and `pnpm-workspace.yaml` already carries `allowBuilds: esbuild`,
so the pinned dependency adds no second copy and no new trust decision.
It is also the smallest tool that covers TSX, ESM, browser platform,
bundling, source maps, and a define-time constant with no plugin
ecosystem. Vite library mode would drag in `@vitejs/plugin-react`, which
the module boundary denies on purpose; `tsc` alone cannot bundle, so its
output would carry bare `react/jsx-runtime` imports no browser resolves.

React is bundled, not externalized. That follows from ADR 0022 rather
than from convenience: `mount()` was made the ABI precisely so React
would not be part of the host contract, and externalizing it would
reverse that through the build system — every host would have to supply
a compatible React, and a standalone host might not use React at all.
The cost is real and accepted: duplicate runtimes and a ~570 KB
unminified artifact. Sharing one runtime later is a build optimization
that cannot change the contract, because the contract is a mount
function.

Output is browser ESM at `es2022`, unminified so an operator can review
what they install, with `process.env.NODE_ENV` substituted — React reads
it at module scope and would otherwise touch a Node global that does not
exist in a browser. The output path is read from the module's own
manifest rather than a build convention, so declared and produced
artifacts cannot drift, and it is validated with the same
`packageRelativePathSchema` discovery enforces, so a build can never
write where discovery would later reject.

`@ekklesia/module-ui-build` owns every option; modules own none. It uses
the existing `tooling` role that modules could already depend on, so this
pass required no boundary relaxation at all. Its `bin` points at a
committed launcher rather than compiled output because pnpm links bins
during install, before Turborepo builds anything — a bin targeting
`dist/cli.js` fails to link on a fresh clone and breaks every module's UI
build in CI. A module with no `entrypoints.ui` is not an error; the CLI
reports nothing to build and exits zero, so one script serves both kinds
of module.

Styling is React inline style objects. A stylesheet import fails the
build rather than emitting a sidecar `.css` that no manifest declares and
no host loads — an undeclared asset would appear to work in tests and
silently do nothing in a real host.

`templates/module` is the canonical example and now ships optional UI.
Its tests build the artifact from source, validate it with
`parseModuleUiExport`, mount it into a real DOM, assert the rendered
output, and unmount it; the artifact is rebuilt per run so the proof can
never pass against stale output, and `dist/` stays gitignored. Because
verify runs both `pnpm test` and `pnpm build`, a UI that cannot be
produced fails CI through two independent paths.

One correction worth stating plainly: the UI TypeScript project declares
`"types": []`, and a UI file referencing `process` does fail in
isolation, but TypeScript still pulls Node globals in transitively — a
file importing `@ekklesia/module-ui-sdk` reaches `@ekklesia/contracts`
and through its Zod and Drizzle types `process.env` typechecks again.
The docs and ADR describe this as the convention it is rather than the
guard it is not.

Core is untouched. Building is an authoring step; discovery still only
validates the artifact a module shipped and never executes or produces
one.

Co-Authored-By: Claude Opus 5 <[email protected]>

docs/architecture/decisions/0022-module-ui-authoring-and-host-contract.md

@@ -228,6 +228,14 @@ a way to smuggle anything else in.
 
 ## Consequences
 
+> **Cross-reference — see [ADR 0023](0023-module-ui-build-pipeline.md).**
+> The gap this section records — that module UI was not buildable end to end, because no pipeline
+> turned `.tsx` into the compiled `entrypoints.ui` artifact — is now closed. ADR 0023 selects
+> esbuild, bundles React rather than externalizing it (preserving this ADR's mount-function ABI),
+> emits browser ESM at the manifest-declared path, and keeps stylesheet imports unsupported by
+> failing the build on one. Everything else in this ADR remains accepted and unchanged.
+
+
 A module author can now write a real screen in React, against a documented four-member host context,
 and know exactly what the artifact must export. Two hosts can consume that artifact with no shared
 code beyond one small package, and the test suite proves it by mounting one fixture artifact under