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/repository-boundaries.md

@@ -8,7 +8,7 @@ These rules map platform ownership to filesystem and package boundaries. The exe
 | `apps/*` | Thin deployable composition roots | Public Core APIs, generated bootstrap, or a surface as required by the app |
 | `core` | Feature-agnostic platform implementations | Public contracts and external infrastructure libraries |
 | `modules/*` | Domain capability, data, and the module's own UI | Module SDK, module UI SDK, public contracts, React, and external backend libraries |
-| `surfaces/*` | UI, renderers, navigation, and interaction | Surface SDK, API/auth clients, public contracts, and design packages |
+| `surfaces/*` | The application shell, UI, renderers, navigation, and interaction | Surface SDK, API/auth clients, the module UI SDK and host loader, design packages, and a browser framework |
 | `builders/*` | Declarative surface composition tooling | Builder/surface SDKs and public contracts |
 | `packages/*` | Explicitly scoped SDKs, contracts, clients, design, testing, or tooling | Only dependencies appropriate to the package's declared level |
 | `templates/module` | A small example backend module | The same dependencies allowed for any module |
@@ -47,7 +47,21 @@ These rules map platform ownership to filesystem and package boundaries. The exe
 - A publication helper accepts module **identity** only. Neither Core's registry nor the API's URL
   builder takes a filename, relative path, or any other artifact selector, so no caller can use one
   to reach a second file inside a module package.
-- A surface never imports Core or a feature module. It uses public API/client contracts.
+- A surface never imports Core or a feature module. It uses public API/client contracts, and reaches
+  the server over HTTP.
+- A surface may depend only on browser-safe shared roles (`api-client`, `auth-client`,
+  `design-tokens`, `module-ui-host`, `module-ui-sdk`, `surface-sdk`, `ui`) plus dev-time `testing`
+  and `tooling`. **`@ekklesia/contracts` is deliberately excluded**, despite being a "public
+  contract" package: its barrel pulls Drizzle's types, and with them Node's global declarations, into
+  any program that imports it — measured in
+  [ADR 0024](decisions/0024-browser-safe-ui-sdk-and-host-loader.md), which removed exactly that
+  import from `@ekklesia/module-ui-sdk` to close the browser boundary. `module-sdk` re-exports the
+  same barrel and is excluded for the same reason. A surface declares its own types for the wire and
+  validates what arrives ([ADR 0026](decisions/0026-minimal-ekklesia-module-ui-host.md)).
+- The browser host (`surfaces/shell`) statically imports no module. Every installed module UI it can
+  mount arrives at run time as a URL from the module UI inventory, is fetched by the generic loader,
+  and is never bundled into the shell. Its own build (esbuild, owned by that package) is a separate
+  concern from `@ekklesia/module-ui-build`, which compiles a *module's* declared artifact.
 - Separate surfaces do not import each other's internals.
 - Builder code composes contracts and surface renderer identifiers; it does not import module or
   surface internals.