fix: fix deep sensitive redaction

[ccharly]

Ancestor branches were still able to keep a reference to the original data that was not redacted, resulting in potentially leaking the sensitive data using custom failure reporting.

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Note

Medium Risk
Changes sensitive-data redaction in error branches; incorrect ancestor patching could still leak secrets or alter failure shapes for custom reporters.

Overview
Fixes a leak where sibling-field validation failures could still expose sensitive values on outer entries in failure.branch, because ancestors kept live references to the unredacted child object.

withRedactedBranch now redacts the matched parent, then walks ancestors backward, copying each level and swapping the child reference for the already-sanitized branch entry. Plain objects, arrays, and Maps are handled separately.

Adds validation fixtures for nested objects, deep nesting, array-wrapped secrets, and Map-wrapped secrets.

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