Telemetry Metrics Export

Writes metrics as JSON lines.

var config = logly.TelemetryConfig.development();
config.metricFormat = .json;
config.metricsFilePath = "telemetry_metrics.jsonl";
var telemetry = try logly.Telemetry.init(allocator, config);
defer telemetry.deinit();

Output:

Metrics exported to telemetry_metrics.jsonl

File preview (telemetry_metrics.jsonl — one JSON object per line):

{ "name": "http.request.duration", "value": 12.5, "kind": "histogram" }