Fix #772 ComputedPartialFailFast

[MateuszKubuszok]

Summary

Closes #772.

Adds fail-fast-aware variants of partial transformer DSL methods. These accept functions that receive a failFast: Boolean parameter, allowing users to optimize partial computations based on whether .transform (collects all errors, failFast = false) or .transformFailFast (stops at first error, failFast = true) was used.

New methods

Added to both PartialTransformerInto and PartialTransformerDefinition (Scala 2.12, 2.13, and 3):

Method	Function signature
withFieldComputedPartialFailFast	(From, Boolean) => partial.Result[U]
withFieldComputedPartialFromFailFast	(S, Boolean) => partial.Result[U]
withSealedSubtypeHandledPartialFailFast	(Subtype, Boolean) => partial.Result[To]
withEnumCaseHandledPartialFailFast	alias for the above
withConstructorPartialFailFast	curried: (a, b, ...) => (failFast: Boolean) => partial.Result[To]
withConstructorPartialToFailFast	curried, with target selector

Example

Foo("value", 10)
  .intoPartial[Bar]
  .withFieldComputedPartialFailFast(_.c, (foo, failFast) =>
    if (failFast) partial.Result.fromValue(foo.b.toLong)      // skip expensive work
    else partial.Result.fromValue(foo.b.toLong * 2)           // full computation
  )
  .transformFailFast // failFast = true

Implementation details

• Type-level entries: ComputedPartialFailFast, ComputedPartialFromFailFast, CaseComputedPartialFailFast, ConstructorPartialFailFast added to TransformerOverrides
• Internal representation: failFastAware: Boolean flag on TransformerOverride.ComputedPartial and ConstructorPartial
• Curried storage: Functions are stored curried (A => Boolean => Result[B]) since chimney-macro-commons only supports Expr.apply for Function1
• Rule modules: TransformProductToProductRuleModule and TransformSealedHierarchyToSealedHierarchyRuleModule updated to thread ctx.failFast when failFastAware = true

Tests

• withFieldComputedPartialFailFast passes correct failFast via transform and transformFailFast
• withFieldComputedPartialFromFailFast variant
• withSealedSubtypeHandledPartialFailFast for sealed hierarchies
• PartialTransformer.define builder variant

Documentation

• New "Fail-fast-aware partial computations" subsection in supported-transformations.md
• Runnable Scala CLI snippet demonstrating failFast flag behavior

[codecov]

Codecov Report

❌ Patch coverage is 66.04651% with 73 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.04%. Comparing base (f71b758) to head (3dfe210).
⚠️ Report is 103 commits behind head on master.

Files with missing lines	Patch %	Lines
...er/rules/TransformProductToProductRuleModule.scala	38.23%	21 Missing ⚠️
...ey/internal/compiletime/ChimneyTypesPlatform.scala	56.25%	14 Missing ⚠️
...letime/derivation/transformer/Configurations.scala	63.88%	13 Missing ⚠️
...ey/internal/compiletime/ChimneyTypesPlatform.scala	76.31%	9 Missing ⚠️
...etime/dsl/PartialTransformerDefinitionMacros.scala	20.00%	8 Missing ⚠️
...compiletime/dsl/PartialTransformerIntoMacros.scala	60.00%	4 Missing ⚠️
...rmSealedHierarchyToSealedHierarchyRuleModule.scala	84.61%	2 Missing ⚠️
...etime/dsl/PartialTransformerDefinitionMacros.scala	90.00%	1 Missing ⚠️
...compiletime/dsl/PartialTransformerIntoMacros.scala	96.87%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #875      +/-   ##
==========================================
- Coverage   86.08%   85.04%   -1.05%     
==========================================
  Files         154      154              
  Lines        6923     7116     +193     
  Branches      779      794      +15     
==========================================
+ Hits         5960     6052      +92     
- Misses        963     1064     +101     

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