Boolean fields missing from fieldTypeMap

Problem

Quickwit's _field_caps endpoint reports boolean fields as type boolean, but the plugin's fieldTypeMap in src/utils/index.ts does not include a boolean entry. This means:

1. Boolean fields get type: undefined when mapped through fieldTypeMap
2. They are excluded from type-filtered field pickers (e.g. when the query editor requests "number" or "string" fields)
3. They may not appear in autocomplete suggestions

Scope

In our OTEL log index, there are 157 boolean fields (dynamic JSON subfields). These are fields like attributes.attr.command.ignoreUnknownIndexOptions that have boolean values in the indexed JSON documents.

Fix

Add boolean to fieldTypeMap:

export const fieldTypeMap: Record<string, string> = {
  // ... existing entries ...
  boolean: 'boolean',
};

May also need to handle boolean in filter operator selection if Grafana passes boolean values as strings.

Start in src/utils/index.ts and inspect fieldTypeMap and the code that maps _field_caps types into field pickers. Add boolean handling and check whether filter operator selection receives boolean values as strings. Done means boolean fields have the expected type, appear in type-filtered pickers and autocomplete suggestions, and filter selection handles them correctly.