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]>

apps/api/tests/module-ui-routes.test.ts

@@ -440,9 +440,10 @@ describe("module UI artifact publication — filesystem exposure", () => {
       // A trailing segment of any kind, including an empty one.
       `${base}/0.1.0/`,
       `${base}/0.1.0/anything`,
-      // Fewer segments than the route declares.
+      // Fewer segments than the route declares. The collection root itself is deliberately absent
+      // from this list: it is the authenticated inventory (ADR 0026) rather than a 404, and is
+      // asserted separately below.
       base,
-      MODULE_UI_ASSET_PREFIX,
     ];
 
     for (const url of unreachable) {
@@ -456,6 +457,21 @@ describe("module UI artifact publication — filesystem exposure", () => {
     }
   });
 
+  it("serves no artifact bytes from the collection root, which is the authenticated inventory", async () => {
+    const { app } = await installWithNeighbours();
+
+    // `/api/v1/module-ui` lists what a host may mount (ADR 0026) and requires
+    // `core.modules.ui.read`; this installation's caller is anonymous, so it is refused. Either way
+    // it never yields a byte of any artifact or neighbouring file.
+    const response = await app.request(MODULE_UI_ASSET_PREFIX);
+    const body = await response.text();
+
+    expect(response.status).toBe(403);
+    expect(body).not.toContain("mount");
+    expect(body).not.toContain("secret");
+    expect(body).not.toContain("internal");
+  });
+
   it("treats a traversal attempt as an ordinary failed lookup", async () => {
     const { app } = await installWithNeighbours();