Create "Masked" validator

[henriquemoody]

The Masked validator decorates other validators to mask sensitive input values in error messages while still validating the original unmasked data.

This validator is essential for applications handling sensitive information such as passwords, credit cards, or email addresses. Without it, users would need to implement a custom layer between Validation and the end user to prevent PII from appearing in error messages or logs.

With Masked, sensitive data protection is built directly into the validation workflow with no additional abstraction required.

[Copilot]

Pull request overview

Adds a new Masked validator that decorates an inner validator to mask the input value used in validation error messages (PII-safe), plus supporting Result input propagation and documentation/tests.

Changes:

• Introduces Masked validator and exposes it through mixin builder/chain APIs (e.g., v::masked(...), nullOrMasked(...), etc.).
• Adds Result::withInput() to propagate masked input through adjacent results and selected child results.
• Adds unit/feature tests, fixtures updates, and documentation for the new validator.

Reviewed changes

Copilot reviewed 28 out of 28 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
tests/unit/Validators/MaskedTest.php	Unit tests for Masked construction, type handling, and masking behavior.
tests/unit/ResultTest.php	Unit tests for new Result::withInput() propagation behavior.
tests/src/TestCase.php	Adds data providers for “string values” vs “non-string values” used by new tests.
tests/src/Stubs/ToStringStub.php	Updates stub to implement Stringable for StringVal-compatible test coverage.
tests/fixtures/data-provider.php	Extends fixture tags to support stringVal-driven data providers and adds a Stringable object case.
tests/feature/Validators/MaskedTest.php	Feature tests verifying masking and error messages via the public API (v::masked).
src/Validators/Masked.php	Implements the new Masked validator using MaskFormatter and StringVal.
src/Result.php	Adds withInput() and refactors adjacent handling to support masked inputs in result trees.
src/Mixins/UndefOrChain.php	Declares undefOrMasked(...) chain method.
src/Mixins/UndefOrBuilder.php	Declares undefOrMasked(...) builder method.
src/Mixins/PropertyChain.php	Declares propertyMasked(...) chain method.
src/Mixins/PropertyBuilder.php	Declares propertyMasked(...) builder method.
src/Mixins/NullOrChain.php	Declares nullOrMasked(...) chain method.
src/Mixins/NullOrBuilder.php	Declares nullOrMasked(...) builder method.
src/Mixins/NotChain.php	Declares notMasked(...) chain method.
src/Mixins/NotBuilder.php	Declares notMasked(...) builder method.
src/Mixins/KeyChain.php	Declares keyMasked(...) chain method.
src/Mixins/KeyBuilder.php	Declares keyMasked(...) builder method.
src/Mixins/Chain.php	Declares base masked(...) chain method.
src/Mixins/Builder.php	Declares base masked(...) builder method.
src/Mixins/AllChain.php	Declares allMasked(...) chain method.
src/Mixins/AllBuilder.php	Declares allMasked(...) builder method.
src-dev/Markdown/Linters/ValidatorHeaderLinter.php	Updates doc linting rules to treat *TextMasker types as special-cased.
src-dev/Commands/LintMixinCommand.php	Updates mixin lint command to handle *TextMasker types and imports str_ends_with.
docs/validators/Masked.md	Adds end-user documentation for the new validator and examples.
docs/validators.md	Adds Masked to the validator index and categorization.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.20%. Comparing base (ec16b3d) to head (882f24b).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1652      +/-   ##
============================================
+ Coverage     99.19%   99.20%   +0.01%     
- Complexity      908      915       +7     
============================================
  Files           190      191       +1     
  Lines          2117     2146      +29     
============================================
+ Hits           2100     2129      +29     
  Misses           17       17              

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