fix(http): preserve batch delete client errors

Let status-coded 4xx errors reach the shared Fastify handler so missing sessions remain distinguishable from transaction failures. Add regression coverage for the missing-session response.

packages/http-routes/src/routes/shared-routes.test.ts

@@ -388,6 +388,22 @@ describe('registerSharedRoutes smoke tests', () => {
     assert.equal(memberCount.count, 2)
   })
 
+  it('POST /_web/sessions/:id/members/batch-delete preserves missing-session errors', async () => {
+    const routeApp = Fastify()
+    registerSharedRoutes(routeApp, createTestContext())
+    await routeApp.ready()
+
+    const resp = await routeApp.inject({
+      method: 'POST',
+      url: '/_web/sessions/missing/members/batch-delete',
+      payload: { memberIds: [1] },
+    })
+
+    await routeApp.close()
+
+    assert.equal(resp.statusCode, 404)
+  })
+
   it('POST /_web/sessions/:id/members/batch-delete rolls back every deletion when one member fails', async () => {
     const db = createSessionDb()
     db.exec(`

packages/http-routes/src/routes/web/members.ts

@@ -64,7 +64,7 @@ export function registerMemberRoutes(server: FastifyInstance, ctx: MemberRouteCo
           throw new Error('Member deletion transaction returned no result')
         }
       } catch (error) {
-        if (apiErrorFromUnknown(error)) throw error
+        if (apiErrorFromUnknown(error) || isHttpClientError(error)) throw error
         appLogger.error('members', 'Batch member deletion failed', error)
         return reply.code(500).send({ success: false, error: 'Failed to delete selected members' })
       }
@@ -94,3 +94,13 @@ export function registerMemberRoutes(server: FastifyInstance, ctx: MemberRouteCo
     }
   )
 }
+
+function isHttpClientError(error: unknown): error is Error & { statusCode: number } {
+  return (
+    error instanceof Error &&
+    'statusCode' in error &&
+    typeof error.statusCode === 'number' &&
+    error.statusCode >= 400 &&
+    error.statusCode < 500
+  )
+}