Introduces a new `$redacted` dynamic variable that wraps its single
argument with `strutils.Redact`, allowing sensitive values (e.g.,
authorization headers, query parameters) to be masked in rule
expressions.
The variable accepts exactly one argument, which may itself be a nested
dynamic variable expression such as `$header(Authorization)` or
`$arg(token)`, enabling patterns like `$redacted($header(Authorization))`.
Adds corresponding tests covering plain string redaction, nested header
and query arg wrapping, and the error case when no argument is provided.
0eba045104