Address PR #222 re-review: fix source-uniqueness detection + coverage/cleanups

MUST-FIX
- isSourceUniqueViolation read the wrong error field: kysely-postgres-js
  (postgres@3.4.8) puts the violated constraint on `constraint_name`, not
  node-postgres' `.constraint`, so a concurrent same-slug+language import's
  23505 was never recognized as a source-collision and surfaced a false
  "name already exists" error. Now read `constraint_name` (with `.constraint`
  as a fallback for other drivers). Fix the faked test fixture (it built the
  error with the same wrong `.constraint` field, masking the bug): it now
  uses `constraint_name`, so the test genuinely exercises the skip path and
  FAILS against the unfixed code.
- Extract the catalog modal's role-state computation into a pure
  `catalogRoleInstallState(role, workspaceRoles, language)` helper (mirrors
  role-launch.ts) and cover it with vitest: import / installed / update /
  same-slug-different-language.

SUGGESTIONS
- Restore IAiRoleUpdateFromCatalogResult as a discriminated union mirroring
  the server; narrow the consumer via `"reason" in result` (the boolean
  discriminant does not narrow under strictNullChecks:false).
- README: add a "How it's served" section documenting AI_AGENT_ROLES_CATALOG_URL
  (remote http(s) base / local path / empty => in-repo folder).
- check.mjs: drop the redundant `const key = slug` alias.
- Cover the reason->message mapping in useUpdateAiRoleFromCatalogMutation
  (4 branches) via renderHook with a mocked service.
- Cover importFromCatalog "bundle not in index" => BadGateway.
- Cover updateFromCatalog "slug in index but missing in bundle file" =>
  not-in-catalog.

ARCHITECTURE
- Extract the shared catalog read prefix: a private `loadBundleById`
  (fetchIndex -> meta -> fetchBundle -> versionMap) reused by getCatalogBundle
  and importFromCatalog, and a `catalogRoleContentFields` mapper shared by the
  import insert and update patch. The three orchestrations and their distinct
  write paths stay separate.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/client/src/features/workspace/components/settings/components/ai-agent-roles-catalog-modal.tsx

@@ -27,6 +27,7 @@ import {
   IAiRoleCatalogBundleSummary,
   IAiRoleCatalogRole,
 } from "@/features/ai-chat/types/ai-chat.types.ts";
+import { catalogRoleInstallState } from "@/features/ai-chat/utils/catalog-role-install-state.ts";
 
 interface AiAgentRolesCatalogModalProps {
   opened: boolean;
@@ -230,19 +231,14 @@ function BundlePanel({
   const updateMutation = useUpdateAiRoleFromCatalogMutation();
 
   // Compute each catalog role's install state against the current workspace
-  // roles: an importable role matched by source.slug + source.language.
+  // roles (matched by source.slug + source.language). The decision lives in the
+  // pure `catalogRoleInstallState` helper so it is unit-tested directly.
   const computed = useMemo(() => {
     const list = bundleQuery.data?.roles ?? [];
-    return list.map((role) => {
-      const installed = roles.find(
-        (r) => r.source?.slug === role.slug && r.source?.language === language,
-      );
-      if (!installed) return { role, state: "import" as const };
-      if ((installed.source?.version ?? 0) >= role.version) {
-        return { role, state: "installed" as const, installed };
-      }
-      return { role, state: "update" as const, installed };
-    });
+    return list.map((role) => ({
+      role,
+      ...catalogRoleInstallState(role, roles, language),
+    }));
   }, [bundleQuery.data, roles, language]);
 
   // Default-check every importable role once the bundle content arrives (unless
@@ -300,17 +296,23 @@ function BundlePanel({
 
         {bundleQuery.data && (
           <Stack gap="xs">
-            {computed.map(({ role, state, installed }) => (
+            {computed.map((entry) => (
               <CatalogRoleRow
-                key={role.slug}
-                role={role}
-                state={state}
-                checked={state === "import" ? !!selected?.has(role.slug) : false}
-                onToggle={(checked) => onToggleSlug(role.slug, checked)}
-                fromVersion={installed?.source?.version}
+                key={entry.role.slug}
+                role={entry.role}
+                state={entry.state}
+                checked={
+                  entry.state === "import"
+                    ? !!selected?.has(entry.role.slug)
+                    : false
+                }
+                onToggle={(checked) => onToggleSlug(entry.role.slug, checked)}
+                fromVersion={
+                  entry.state === "update" ? entry.fromVersion : undefined
+                }
                 onUpdate={
-                  state === "update" && installed
-                    ? () => updateMutation.mutate(installed.id)
+                  entry.state === "update"
+                    ? () => updateMutation.mutate(entry.installed.id)
                     : undefined
                 }
                 updating={updateMutation.isPending}