[Feature]: DataCollector should collect unique_id by default

### 🤔 Problem Description

When collecting agent reporters (e.g., wealth), the current implementation only collects the values of the requested column but not the unique agent IDs. This makes it difficult to trace values back to the corresponding agent, especially when debugging, analyzing distributions, or joining with other data sources.

Without unique IDs, it’s unclear which agent each value belongs to, leading to ambiguity and potential data misalignment.

### 💡 Proposed Solution

_No response_

### 🔄 Alternatives Considered

_No response_

### ➕ Additional Context

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Start by locating the DataCollector entry point and the agent reporter collection path. Verify how requested columns are currently gathered, then define done as collecting each agent's unique_id by default alongside the requested values and add or update coverage for that behavior if tests are present.

Written by the indexing model from the issue text.