[BUGFIX] Loki: dispatch to instant query when context.mode is instant

[tgitelman]

Summary

Ref: perses/perses#4270

getLokiTimeSeriesData() always calls client.queryRange() regardless of context.mode. When a panel requests instant mode (e.g. Table without column plugins), the Loki plugin ignores it and sends query_range — unlike the Prometheus plugin which checks context.mode and dispatches to instantQuery() vs rangeQuery().

This also causes empty results for large time ranges (14d+): query_range with large range vectors triggers Loki's split_queries_by_interval, which truncates lookback windows. The instant endpoint (/loki/api/v1/query) does not split and evaluates correctly.

Changes

loki/src/queries/loki-time-series-query/get-loki-time-series-data.ts:

• Check context.mode — dispatch to client.query() (/loki/api/v1/query) for instant mode
• Added convertVectorToTimeSeries() to convert instant query vector responses to the TimeSeries format
• streams resultType (raw log queries without aggregation) returns empty — not applicable for time series panels
• Range query path completely unchanged

loki/src/queries/loki-time-series-query/loki-time-series-query-types.ts:

• Updated LokiTimeSeriesQueryResponse to include LokiQueryResponse (instant query responses)

Reproduction

1. Create a dashboard with a LokiDatasource
2. Add a Table panel (no column plugins) with count_over_time(... [$__range])
3. Enable Loki gateway debug logs (--log.level=debug)
4. Before fix: 100% of requests are /loki/api/v1/query_range, zero instant queries
5. After fix: Table requests go to /loki/api/v1/query
6. Select "Last 14 days" — before fix: empty results; after fix: correct totals

Test plan

• Loki gateway logs show /loki/api/v1/query (instant) requests when Table panel loads
• Large time ranges (14d+) return correct data instead of empty results
• Range queries (time series charts) continue working unchanged
• Aggregation queries (count_over_time, sum_over_time) return correct single values
• Raw log queries (no aggregation) in instant mode return empty gracefully