Goal / Objective                                                                                          

Ensure that all QI stages that read internalQuerySpillingMinAvailableDiskSpaceBytes see a consistent, snapshotted value for the full lifetime of a query. The value must be read once (at query initialization or stage construction) and held stable — not re-read from the underlying atomic on each spill or each stage — so that multiple spilling stages within the same query (e.g., two $sort stages, a $group  and a $lookup) all operate against the same threshold.

Context & Background

 internalQuerySpillingMinAvailableDiskSpaceBytes is an AtomicWord<long long> server parameter (default 500
  MB) that controls the minimum free disk space required before any spilling is permitted. Because it is an atomic, it can be read by calling .load()/.loadRelaxed() anywhere in the codebase. However, calling this way means we don't get a consistent internalQuerySpillingMinAvailableDiskSpaceBytes throughout a query.

Call sites that should be considered to be updated

  The following query-intergration-owned call sites currently call .load() directly on
  internalQuerySpillingMinAvailableDiskSpaceBytes and must be replaced with the appropriate snapshotted access
   pattern:

  File: src/mongo/db/exec/classic/near.cpp
  Location: FileBasedSorterSpiller construction
  Recommended fix: expCtx->getQueryKnobConfiguration().getInternalQuerySpillingMinAvailableDiskSpaceBytes()

  File: src/mongo/db/exec/classic/text_or.cpp
  Location: Two FileBasedSorterSpiller constructions
  Recommended fix: expCtx()->getQueryKnobConfiguration().getInternalQuerySpillingMinAvailableDiskSpaceBytes()

Acceptance Criteria

All QI-owned stages have internalQuerySpillingMinAvailableDiskSpaceBytes see a consistent, snapshotted value for the full lifetime of a query, and to each sorter instance a QI stage constructs.

Behavioral expectations
  - With default parameter settings, observable behavior of spilling is unchanged.
  - All stages within a single query use the same threshold value, regardless of when their spill operations occur relative to one another.