perf: multiple performance improvements during pre-testing stages

[hugo-vrijswijk]

• perf(core): use all cores for parsing, mutating and copying files
• perf(core): render mutated files inside the parallel stage
• perf(core): avoid pretty-printing trees for structural equality
• perf(core): cache reprinted syntax of substitution mutations
• perf(testrunner): skip logging per-mutant test-run messages
• perf(sbt): gate debug logs by configured log level
• perf(logging): cache colorEnabled instead of recomputing it per log line
• perf(core): slim down per-mutant debug log message

[mergify]

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[Copilot]

Pull request overview

This PR focuses on reducing overhead in Stryker4s’ hot paths by increasing parallelism for CPU-bound stages, avoiding repeated expensive string/tree rendering, and cutting down on per-mutant logging work across runners and build-tool integrations.

Changes:

• Parallelize parsing/mutating/copying/writing work using all available CPU cores, and move mutated-file rendering into the parallel stage.
• Reduce expensive debug/log rendering (skip per-mutant StartTestRun logging; slim down per-mutant debug messages; cache colorEnabled; cache substitution mutation syntax).
• Replace Tree.structure-based equality with a custom structural comparator that ignores positions, with added tests.

Reviewed changes

Copilot reviewed 21 out of 21 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
modules/testRunner/src/main/scala/stryker4s/testrunner/server/UnixSocketServer.scala	Avoids logging StartTestRun requests to reduce per-mutant overhead.
modules/testRunner/src/main/scala/stryker4s/testrunner/server/TcpSocketServer.scala	Avoids logging StartTestRun requests to reduce per-mutant overhead.
modules/testkit/src/main/scala/stryker4s/testkit/TestLogger.scala	Switches colorEnabled to lazy to align with cached evaluation.
modules/sbt/src/main/scala/stryker4s/sbt/Stryker4sPlugin.scala	Passes sbt logLevel through to the logger to gate debug output.
modules/sbt/src/main/scala/stryker4s/log/SbtLogger.scala	Gates logging by configured minimum sbt level; caches color detection.
modules/mill/src/main/scala/stryker4s/log/MillLogger.scala	Caches color detection instead of recomputing per log line.
modules/core/src/test/scala/stryker4s/run/MutantRunnerTest.scala	Updates expectations for the new, slimmer per-mutant debug message format.
modules/core/src/test/scala/stryker4s/report/mapper/MutantRunResultMapperTest.scala	Updates to use cached substitution mutation syntax.
modules/core/src/test/scala/stryker4s/extension/TreeExtensionsTest.scala	Adds tests for the new treeEq structural equality behavior.
modules/core/src/main/scala/stryker4s/run/MutantRunner.scala	Uses CPU-parallelism for file copying/writing; moves mutated file rendering into parallel work; slims debug logging.
modules/core/src/main/scala/stryker4s/mutation/MutationTypes.scala	Caches tree.reprint() for substitution mutations (treeSyntax).
modules/core/src/main/scala/stryker4s/mutants/Mutator.scala	Uses CPU-parallelism for parsing/mutating/instrumenting stages.
modules/core/src/main/scala/stryker4s/mutants/findmutants/MutantMatcher.scala	Uses cached substitution syntax when available; avoids expensive equality checks when eq suffices.
modules/core/src/main/scala/stryker4s/extension/TreeExtensions.scala	Replaces Tree.structure equality with a custom structural comparator ignoring positions.
modules/core/src/main/scala/stryker4s/config/Config.scala	Introduces cpuParallelism as “all cores” parallelism for local CPU-bound work.
modules/api/src/main/scala/stryker4s/log/Logger.scala	Caches colorEnabled instead of recomputing it for every log line.
maven/src/test/scala/stryker4s/maven/runner/ZincCompilerTest.scala	Adapts tests to use fs2.io.file.Path for jar paths.
maven/src/main/scala/stryker4s/maven/Stryker4sMavenRunner.scala	Adapts to resolver APIs returning Path instead of File.
maven/src/main/scala/stryker4s/maven/runner/ZincCompiler.scala	Adapts compiler/bridge resolution to Path APIs; converts to File where needed by Zinc.
maven/src/main/scala/stryker4s/maven/runner/ArtifactResolver.scala	Switches artifact resolution APIs to return fs2.io.file.Path.
maven/src/main/scala/stryker4s/log/MavenMojoLogger.scala	Caches colorEnabled instead of recomputing it for every log line.

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