Fix SegmentPurger to prevent unintended star-tree modification during purge

## Problem

When PurgeTask rebuilds a segment (after purging compliance/late-event records), SegmentPurger creates a new segment via SegmentGeneratorConfig which unconditionally picks up starTreeIndexConfigs from the table config, even if enableDynamicStarTreeCreation is set to false. This causes segments to unexpectedly gain star-tree indexes during purge, even when enableDynamicStarTreeCreation is false.

## Proposal

Makes SegmentPurger.initSegmentGeneratorConfig() respect enableDynamicStarTreeCreation — if it's false (default), star-tree configs should not be updated/deleted

Start in SegmentPurger.initSegmentGeneratorConfig() and trace how PurgeTask uses SegmentGeneratorConfig and table configuration when rebuilding a segment. Verify the behavior with enableDynamicStarTreeCreation both false and true; done means purge does not update or delete star-tree configs when the setting is false.

Written by the indexing model from the issue text.