fix(fn-runtime): meta client must use X-Meta-Schema, not X-Api-Name

The meta GraphQLClient created in createClients() is used for queries
against platform-level data (databases, sites, domains, themes — tables
in metaschema_public). It should NOT use tenant API routing.

Sending X-Api-Name: <name> causes the server to look up every schema
registered for that API in services_public.api_schemas. The 'private'
API in particular is registered (per metaschema_generators.provision_database_apis)
with both the *_public and *_private variants of every module schema.
graphile-build-pg then tries to introspect all of them, finds tables
that exist under the same name in two schemas (e.g. identity_providers
in both constructive_auth_public and constructive_auth_private), and
fails the schema build with:

  Error: Attempted to add a second codec named 'identityProviders'
  (existing: RecordCodec(identityProviders), new: RecordCodec(identityProviders))

After the schema build fails, every request to that server returns a
500 'Unknown error occurred', so functions calling GetDatabaseInfo via
the meta client get back nothing usable.

The correct routing for platform data is X-Meta-Schema: true, which
takes the schema list from API_META_SCHEMAS env var rather than
querying the DB. This matches the routing the older in-monorepo
implementation used (see constructive/functions/send-email-link/src/index.ts
on the constructive repo). The detail was lost during the extraction
into this repo.

Bug present since the initial setup commit (272763a, 2026-02-11) but
not exercised until consumers (e.g. constructive-hub) started loading
this fn-runtime instead of the in-monorepo function.

Author: Anmol1696

packages/fn-runtime/src/graphql.ts

@@ -61,11 +61,14 @@ export const createClients = (
     ...(schemata && { schemata })
   });
 
+  // Meta client targets platform-level data (databases, sites, domains, themes
+  // in metaschema_public). It must NOT use tenant API routing — sending
+  // X-Api-Name causes the server to load every schema registered for that API
+  // (both *_public and *_private variants), which collides on duplicate codec
+  // names like identityProviders. Use X-Meta-Schema instead.
   const meta = createGraphQLClient(metaGraphqlUrl, env, {
     hostHeaderEnvVar: 'META_GRAPHQL_HOST_HEADER',
-    databaseId,
-    ...(apiName && { apiName }),
-    ...(schemata && { schemata })
+    useMetaSchema: true,
   });
 
   return { client, meta };