fix: Register all sealed segments’ BM25 stats in IDFOracle (#46726)

If QueryNode loads multiple sealed segments with BM25 enabled, BM25
stats registration into IDFOracle could stop after the first segment due
to an early-terminating ConcurrentMap.Range callback. This change:
Register BM25 stats for all sealed segments by continuing iteration
(return true) during sealed-segment load
Prevent repeated warnings like idf oracle lack some sealed segment
Ensure IDF/BM25 statistics are not silently incomplete (improving BM25
ranking correctness)
issue: #46725 
Core invariant: for any BM25-enabled collection, every loaded sealed
segment with available BM25 stats must be registered into IDFOracle, so
SyncDistribution can always find the sealed segments present in the
distribution snapshot.
Bug fix: ConcurrentMap.Range respects the callback’s boolean return;
returning false stops iteration. The sealed BM25 stats registration
callback previously returned false, which could register only the first
sealed segment and leave the rest missing—causing IDFOracle to warn idf
oracle lack some sealed segment and potentially compute IDF from
incomplete stats. Fixed by returning true to continue iterating and
registering all segments.
No behavior regression: the change only affects the sealed-segment BM25
stats registration loop; it does not alter segment loading, distribution
snapshot generation, or non-BM25 codepaths. For collections without BM25
(or when BM25 stats are nil), behavior remains unchanged.

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
- Core invariant: For any BM25-enabled collection, every loaded sealed
segment with available BM25 stats must be registered into IDFOracle so
SyncDistribution can discover them in distribution snapshots.

- Bug fix (links to #46725): The BM25 stats registration callback used
with bm25Stats.Range() in loadStreamDelete() returned false, which
prematurely stopped iteration after the first sealed segment and left
subsequent sealed segments unregistered. The fix changes the callback to
return true so the Range loop completes and registers BM25 stats for all
sealed segments.

- Logic simplified/removed: The early-return (false) in the
ConcurrentMap.Range callback that aborted further registrations has been
removed (replaced by returning true). That early abort was redundant and
incorrect because registration must proceed for every entry; allowing
Range to continue restores the intended one-to-many registration
behavior.

- No data loss or regression: The change is narrowly scoped to the
sealed-segment BM25 stats registration loop in
internal/querynodev2/delegator/delegator_data.go and does not modify
segment loading, distribution snapshot generation, growing-segment
handling, or non-BM25 codepaths. Returning true only permits full
iteration and registration; it does not delete or alter existing data
structures or load state, so IDF/BM25 statistics become complete without
changing other behaviors.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Signed-off-by: thangTang <tangtianhang099@gmail.com>

internal/querynodev2/delegator/delegator_data.go

@@ -760,7 +760,8 @@ func (sd *shardDelegator) loadStreamDelete(ctx context.Context,
 				zap.Int64("segmentID", segmentID),
 			)
 			sd.idfOracle.Register(segmentID, stats, segments.SegmentTypeSealed)
-			return false
+			// continue iterating to register all segments' stats
+			return true
 		})
 	}