Fix disable:next handling in multiline strings

[EhsanAzish80]

Fixes #2645.

disable:next was consumed by the first physical line break inside a multiline string, allowing disabled rules such as wrap to run on the remaining string contents.

This change evaluates rule enablement within multiline strings from the opening delimiter, including content inside string interpolation scopes. The directive therefore applies to the entire multiline string while formatting resumes normally afterward.

Added focused regression coverage that reproduces the unwanted wrapping and verifies formatting resumes after the string.

Testing:

• Full test suite: 5,930 tests passed with zero failures
• Changed files pass SwiftFormat lint

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.45%. Comparing base (dac0c06) to head (7981f2f).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #2646   +/-   ##
========================================
  Coverage    95.44%   95.45%           
========================================
  Files          177      177           
  Lines        27073    27095   +22     
========================================
+ Hits         25841    25864   +23     
+ Misses        1232     1231    -1     

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[nicklockwood]

@EhsanAzish80 thanks! and sorry for the delay in review