Summary

• add interpreter regression coverage for recent map runtime edge cases
• add parser coverage for nested and invalid map[...] type syntax

Changed paths tested

• interp/map.go / interp/threaded.go
• types/parse.go

Added tests

• MAP_GET returns the same entry for -0.0 and 0.0 float keys
• MAP_NEW keeps the last value when duplicate keys are provided
• types.Parse handles nested bracketed map keys and rejects missing key/elem map syntax

Validation

• go test ./types
• go test ./interp

Skipped targets

• map ref/string retain-release branches: behavior is clear but would require heap-lifetime assertions with higher setup cost than this narrow coverage task
• docs and opcode metadata files: already exercised indirectly by existing type/opcode tests and not a behavior gap for this change