Array-of-tables AST structure incorrect in edge cases

[gildor]

Summary

Several array-of-tables patterns produce an incorrect AST tree — tables appear as plain objects where arrays are expected, or vice versa. This affects implicit array creation and mixed table/array-of-tables patterns.

Affected toml-test cases (5)

Found via toml-lang/toml-test compliance suite:

• valid/array/open-parent-table.toml — implicit parent of array-of-tables
• valid/table/array-implicit.toml — implicitly created array
• valid/table/array-implicit-and-explicit-after.toml — implicit then explicit
• valid/table/array-table-array.toml — array inside array-of-tables
• valid/table/array-empty-name.toml — array-of-tables with empty key [[""]]

Related: #32