fix(query-orchestrator): Return cached result when refreshKey changes during must-revalidate

[ovr]

When refreshKey changes faster than the query executes (e.g. SELECT NOW() with a slow query), must-revalidate gets stuck in an endless Continue wait loop. Each time the query finishes, the refreshKey has already changed — so it re-runs the query, which never catches up.

Fix:

Track which request produced the cached result. If the same request flow already has a result in cache but the refreshKey changed during execution — return the cached data immediately and refresh in the background, instead of blocking and re-executing.

[codecov]

Codecov Report

❌ Patch coverage is 76.92308% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 57.71%. Comparing base (018952a) to head (766bb84).
⚠️ Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
...-query-orchestrator/src/orchestrator/QueryCache.ts	72.72%	2 Missing and 1 partial ⚠️

❗ There is a different number of reports uploaded between BASE (018952a) and HEAD (766bb84). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (018952a)	HEAD (766bb84)
cubesql	1	0

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #10489       +/-   ##
===========================================
- Coverage   83.39%   57.71%   -25.69%     
===========================================
  Files         250      223       -27     
  Lines       75112    17519    -57593     
  Branches        0     3604     +3604     
===========================================
- Hits        62642    10111    -52531     
+ Misses      12470     6866     -5604     
- Partials        0      542      +542     

Flag	Coverage Δ
cube-backend	57.71% <76.92%> (?)
cubesql	?

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