feat: mount discovered module UI in a minimal Ekklesia browser host

Phase 6C pass 2. Every link in the module UI chain existed except the one
that closes it: a module could be authored, built, validated, published at a
browser URL, and loaded by a generic loader — and nothing in Ekklesia did any
of it. There was no browser application at all.

Two pieces were missing. A browser could not discover what to mount, and it
must not work that out for itself.

GET /api/v1/module-ui is the inventory: per publishable module, its id and
version, the server-produced artifact URL, the server-produced root of the
module's own API, and the subset of that module's declared permissions the
caller holds. Five fields, each because building a ModuleUiHostContext needs
it — no filesystem paths, and no name/icon/folder/order, because navigation
metadata is a design that does not exist yet. Its module set is the ADR 0025
publication registry rather than a rescan, so the inventory and the artifact
route cannot disagree. It requires a new Core permission, core.modules.ui.read
(baseline authenticated), because it is precisely the enumeration the anonymous
artifact route deliberately withholds.

Both URLs are server-produced. moduleUiArtifactUrl already existed;
moduleApiBaseUrl is now exported and moduleRoutePath builds on it, so each URL
shape has exactly one author. Without it the shell would hardcode
/api/v1/modules/<id> — the prefix ADR 0022 forbids a module UI from spelling,
reappearing in the host instead.

surfaces/shell (@ekklesia/shell) is the repository's first surface: a small
React application built to static files by its own esbuild script. It resolves
the principal, fetches the inventory, builds the host context entirely from
server-derived data, and hands the artifact URL to @ekklesia/module-ui-host.
One frame per selection — keyed by module identity — defeats the stale-load
race; the host owns the container, the loading state, and every failure, so a
broken module costs its own panel rather than the shell.

The shell statically imports no module, and both levels are checked: no source
import may name a module, and the emitted bundle must contain exactly one
dynamic import (the loader's) with no module id, no /api/v1/modules, no eval,
and no blob URL. Permission hints come from Core's own evaluator and stay
presentation-only — the end-to-end test has a UI holding no grant call its API
anyway and still receive 403.

Surfaces may now depend only on browser-safe shared roles; @ekklesia/contracts
is deliberately excluded, since its barrel pulls Drizzle's types and Node's
globals into the browser — the hole ADR 0024 closed one layer down.

Not the Dashboard: no navigation, grouping, icons, ordering, design system, or
routing. The selector is a list of module ids.

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

docs/architecture/platform-architecture.md

@@ -240,9 +240,36 @@ so the route is not an enumeration oracle. Caching is `no-cache` with a strong `
 `immutable`, because without an installer a version can be rebuilt with different bytes. The server
 reads and writes bytes; it never imports, evaluates, or transforms the artifact.
 
-**A host could now obtain a URL, and nothing uses one.** There is no Dashboard shell, no navigation,
-no module metadata endpoint, and no code that calls the URL helper outside its own tests. A design
-system, stylesheet and general asset publication, and the standalone host remain future work.
+**Phase 6C pass 2 builds the browser host that consumes it.**
+[ADR 0026](decisions/0026-minimal-ekklesia-module-ui-host.md) adds `surfaces/shell`
+(`@ekklesia/shell`), the repository's first surface: a small React application, built to static files
+by its own esbuild script, that discovers installed module UIs and mounts them.
+
+The missing piece was discovery. `GET /api/v1/module-ui` — the collection root of the same prefix the
+artifact route already owns — returns, per publishable module, its id and version, the server-produced
+artifact URL, the server-produced root of the module's own API, and the subset of that module's
+declared permissions the caller actually holds. Nothing else: no filesystem paths, and no display or
+navigation metadata, since ADR 0021 keeps Dashboard grouping an administrator's presentation
+configuration. The module set is the publication registry, never a rescan, so the inventory and the
+artifact route cannot disagree. It requires `core.modules.ui.read` (baseline `authenticated`) because
+it is precisely the enumeration ADR 0025 withheld from the anonymous artifact route.
+
+Both URLs being server-produced is the load-bearing part. `moduleUiArtifactUrl` and the newly exported
+`moduleApiBaseUrl` are each the single construction of their URL shape, so the browser is a consumer
+of both — it never rebuilds `/api/v1/modules/<id>`, the prefix ADR 0022 forbids a module UI from
+spelling, and neither prefix is pinned by having a second author.
+
+The shell builds a `ModuleUiHostContext` entirely from server-derived data, resolves a module's
+relative API calls onto its own API root (refusing anything that escapes it), and hands the artifact
+URL to `@ekklesia/module-ui-host`. It statically imports no module: one frame per selection defeats
+the stale-load race, the host owns the container and every loading and error state, and the bundle is
+checked to contain exactly one dynamic import with no module identity baked in. Permission hints come
+from Core's own evaluator and stay presentation-only — server authorization is proven unchanged by a
+test in which a UI holding no grant calls its API anyway and is refused.
+
+**This is not the Dashboard.** No navigation, grouping, icons, ordering, design system, or routing;
+the selector lists module ids. A production CSP and a deployment for the built shell, sign-in UI,
+general asset publication, and the standalone host remain future work.
 Restart-based discovery, explicit operator-invoked migrations, and the trusted compiled-module model
 are all unchanged.