Remove test warning suppressions, fix all resulting warnings

[halotukozak]

Summary

• Remove Test / scalacOptions --= that suppressed -Wunused:patvars and -Xlint:constant in tests
• Remove Scala 3 -Werror blanket disable
• Fix all resulting compiler warnings in source and test code:
  • Add : Unit type ascriptions to discard-value expressions (conn.pop(), p.trySuccess(), cursor.next(), future.get(), pf(r), buffer.offer())
  • Add : @unchecked to irrefutable pattern matches (val Some(...) = ..., val x :: xs = ..., val CompositeException(...) = ...)
  • Replace unused for-loop variables (for (i <-) with wildcards (for (_ <-) across 12 test files
  • Replace Long.MaxValue + 1 constant overflow with Long.MinValue equivalent

Note: 4 thread.getId deprecation warnings remain — these will be addressed separately.

Test plan

• sbt +test passes for all modules except executionJVM/Compile (pre-existing getId deprecation)
• Verify no behavioral changes in overflow-related OrderedCancelableSuite tests

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR tightens compiler hygiene by removing test-only warning suppressions and re-enabling Scala 3 “fatal warnings” behavior, then updating production and test code to compile cleanly under stricter warning settings.

Changes:

• Removed Test / scalacOptions --= suppressions for -Wunused:patvars and -Xlint:constant, and removed the Scala 3 -Werror exclusion in build.sbt.
• Updated code to explicitly discard values (: Unit) where results are intentionally ignored, and silenced irrefutable-pattern warnings (: @unchecked) where intended.
• Cleaned up tests to avoid unused loop variables and replaced constant-overflow expressions with equivalent non-overflowing literals.

Reviewed changes

Copilot reviewed 22 out of 23 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
monix-tail/shared/src/main/scala/monix/tail/internal/IterantTakeLast.scala	Discard buffer.offer results explicitly to satisfy non-Unit statement warnings.
monix-tail/shared/src/main/scala/monix/tail/internal/IterantCompleteL.scala	Discard cursor.next() results explicitly during cursor draining.
monix-reactive/shared/src/test/scala/monix/reactive/subjects/ReplaySubjectSuite.scala	Replace unused loop variable with wildcard in subscription loops.
monix-reactive/shared/src/test/scala/monix/reactive/subjects/PublishSubjectSuite.scala	Replace unused loop variable with wildcard in subscription loops.
monix-reactive/shared/src/test/scala/monix/reactive/subjects/ProfunctorSubjectSuite.scala	Replace unused loop variable with wildcard in subscription loops.
monix-reactive/shared/src/test/scala/monix/reactive/subjects/BehaviorSubjectSuite.scala	Replace unused loop variable with wildcard in subscription loops.
monix-reactive/shared/src/test/scala/monix/reactive/internal/rstreams/MonixSubscriberAsReactiveSuite.scala	Replace unused loop variable with wildcard in stress loop.
monix-reactive/shared/src/test/scala/monix/reactive/internal/operators/BufferIntrospectiveSuite.scala	Replace unused loop variable with wildcard in repeated onNext loop.
monix-execution/shared/src/test/scala/monix/execution/schedulers/ExecutionModelSuite.scala	Replace unused loop variable with wildcard in frame-advance loop.
monix-execution/shared/src/test/scala/monix/execution/cancelables/OrderedCancelableSuite.scala	Replace constant-overflow expressions with equivalent Long.MinValue values.
monix-execution/shared/src/test/scala/monix/execution/CancelableSuite.scala	Add : @unchecked to suppress irrefutable-pattern warnings in tests.
monix-execution/shared/src/main/scala/monix/execution/CancelablePromise.scala	Add : @unchecked to suppress irrefutable-pattern warning when destructuring a non-empty list.
monix-execution/shared/src/main/scala/monix/execution/CancelableFuture.scala	Discard pf(r) result explicitly in andThen.
monix-execution/shared/src/main/scala/monix/execution/Ack.scala	Discard Promise.trySuccess boolean result explicitly.
monix-execution/jvm/src/test/scala/monix/execution/atomic/ConcurrentAtomicSuite.scala	Replace unused loop variables with wildcards in concurrent tests.
monix-execution/jvm/src/test/scala/monix/execution/atomic/ConcurrentAtomicNumberSuite.scala	Replace unused loop variables with wildcards in concurrent tests.
monix-execution/jvm/src/main/scala/monix/execution/schedulers/AdaptedThreadPoolExecutor.scala	Discard future.get() result explicitly in afterExecute.
monix-eval/shared/src/test/scala/monix/eval/TaskMemoizeOnSuccessSuite.scala	Replace unused loop variables with wildcards in stack-safety loops.
monix-eval/shared/src/test/scala/monix/eval/TaskExecuteWithOptionsSuite.scala	Add : @unchecked to suppress irrefutable-pattern warning when destructuring f.value.
monix-eval/shared/src/main/scala/monix/eval/internal/TaskFromFuture.scala	Discard conn.pop() result explicitly.
monix-eval/shared/src/main/scala/monix/eval/internal/TaskCreate.scala	Discard ctx.connection.pop() result explicitly.
monix-eval/shared/src/main/scala/monix/eval/internal/TaskConversions.scala	Discard conn.pop() result explicitly.
build.sbt	Removes test warning suppressions and the Scala 3 -Werror exclusion.

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