fix: guard copyExportedFields against nil interface values in slices, maps, and pointers

[Copilot]

copyExportedFields panics when encountering nil interface elements inside slices, maps, or pointer targets. reflect.ValueOf(nil) returns a zero reflect.Value; calling .Set() with it panics. Discovered by the rapid-based fuzz test TestNilSafetyExportedValues.

panic after 72 tests: reflect: call of reflect.Value.Set on zero Value

draw a: []interface {}{interface {}(nil), 0, "hello", interface {}(nil)}
draw b: []interface {}(nil)

Changes

• internal/assertions/equal.go — Add nil guards after each recursive copyExportedFields call in the slice/array, map, and pointer branches. Nil results skip Set, preserving the zero value (correct semantics: nil interface has no exported fields).
• Remove stale rapid fail file for TestNilSafetyExportedValues.
• Regenerated docs via go generate ./... (line number shifts from recent changes).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (master@57d0e4e). Learn more about missing BASE report.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #127   +/-   ##
=========================================
  Coverage          ?   91.66%           
=========================================
  Files             ?       97           
  Lines             ?    12623           
  Branches          ?        0           
=========================================
  Hits              ?    11571           
  Misses            ?      828           
  Partials          ?      224           

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