refactor: decouple Vido-specific metadata parsing from getFeatureId

[wazolab]

Severity

P3 — Architecture

Description

`getFeatureId` in `src/utils/index.ts:36-45` contains Vido-specific logic to parse `properties.metadata` as a JSON string:
```ts
// Vido support: shouldn't be part of this plugin
let metadata = feature.properties.metadata
if (typeof metadata === 'string') {
try {
metadata = JSON.parse(metadata)
}
catch {
metadata = undefined
}
}
```

The comment already acknowledges this doesn't belong here. This couples a generic clustering library to a specific data provider's format.

Suggested Approach

Add a `getFeatureId` option to `TeritorioClusterOptions`:
```ts
getFeatureId?: (feature: GeoJSONFeature) => string
```

Default implementation:
```ts
(feature) => {
if (feature.properties.cluster) {
if (!feature.id) throw new Error('Cluster feature is missing "id".')
return feature.id.toString()
}
return (feature.properties?.id ?? feature.id).toString()
}
```

Vido consumers would provide their own implementation that handles the metadata JSON parsing.

Impact

This is a breaking change for Vido consumers who rely on the implicit metadata parsing. Coordinate with Vido team.

Files

• `src/utils/index.ts:29-48`
• `src/types.ts` (add option type)
• `src/teritorio-cluster.ts` (wire up the option)