[Bug] Validation silently passes for nested Map subdocuments loaded via init()

[AbdelrahmanHafez]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the bug has not already been reported

Mongoose version

9.1.3

Node.js version

22.x

MongoDB server version

N/A

Typescript version (if applicable)

N/A

Description

re #15678 #15682

When a document with nested Maps (Map of subdocuments containing another Map) is loaded from the database via init(), validation silently passes for invalid data.

Steps to Reproduce

const mongoose = require('mongoose');

const employeeSchema = new mongoose.Schema({
  name: { type: String, required: true, minlength: 2 }
});

const teamSchema = new mongoose.Schema({
  employees: { type: Map, of: employeeSchema }
});

const companySchema = new mongoose.Schema({
  teams: { type: Map, of: teamSchema }
});

const Company = mongoose.model('Company', companySchema);

// Simulate loading from database via init()
const company = new Company();
company.init({
  _id: new mongoose.Types.ObjectId(),
  teams: {
    engineering: {
      employees: {
        john: { name: 'X' }  // Invalid: minlength is 2, 'X' has length 1
      }
    }
  }
});

// Validation should fail but passes silently
company.validate()
  .then(() => console.log('Validation passed (BUG - should have failed)'))
  .catch(err => console.log('Validation failed:', err.message));

Comparison with constructor (works correctly):

const company2 = new Company({
  teams: {
    engineering: {
      employees: {
        john: { name: 'X' }
      }
    }
  }
});

company2.validate()
  .then(() => console.log('Validation passed'))
  .catch(err => console.log('Validation failed:', err.message));
// Correctly fails with minlength validation error

Expected Behavior

Validation should fail with a minlength error for the name field

Documents loaded from the database (via init()) should behave identically to documents created via the constructor.