fix: align identity events with mParticle batch schema

[khushi1033]

Summary##

Refactors identity events to use the mParticle batch event schema format ({ event_type, data })

Event types are mapped per the Rokt Brain Data Model:

• onLoginComplete → login
• onLogoutComplete → logout
• onModifyComplete → modify_user
• onUserIdentified → identify

MPID and UserIdentities are removed from individual events — they're already on the batch envelope (batch.mpid, batch.user_identities) and don't need to be duplicated per-event. EventDataType and EventCategory are dropped as mParticle SDK internals with no Rokt equivalent.

Before:

{
  "EventName": "login",
  "EventDataType": 14,
  "EventCategory": 0,
  "Timestamp": 1775491325250,
  "MPID": "861148",
  "SessionId": "1EA1DFD3",
  "UserIdentities": { "email": "jenny@rokt.com" }
}

After:

{
  "mpid": "8611485194723014758",
  "user_identities": {
    "customer_id": "2caa7a4d007b44139e0e17b7a23ac7fb",
    "email": "jenny.smith@rokt.com",
    "other_id_6": "CDID1.9.8921.1744745313237"
  },
  // ... rest of batch payload (user_attributes, consent_state, device_info, etc.)
  "events": [
    {
      "event_type": "login",
      "data": {
        "timestamp_unixtime_ms": 1775491325250,
        "session_uuid": "1EA1DFD3-0FBA-42F5-9FA9-6301AA4FC784",
        "mpid": "8611485194723014758"
      }
    }
  ]
}

Testing Plan

• 170/170 Vitest tests pass (lint and build clean)
• Updated 5 identity event test assertions to validate new shape (event_type, data.timestamp_unixtime_ms)
• Tests cover: correct event_type per callback, merge into outgoing batches, queue flush on kit init, and queue cleared after send

[mparticle-automation]

🎉 This PR is included in version 1.24.1 🎉

The release is available on:

• v1.24.1
• GitHub release

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