Module decoder 

TOON v3.0 Decoder — converts TOON back into JSON.

The decoder parses indentation-based TOON structure back into a serde_json::Value tree. It handles all TOON v3.0 constructs:

• Flat and nested objects (indentation-based)
• Inline primitive arrays (key[N]: v1,v2)
• Tabular arrays (key[N]{f1,f2}:\n v1,v2)
• Expanded lists (key[N]:\n - item)
• Quoted/unquoted keys and values with escape sequences
• Type inference: unquoted true/false → bool, null → null, numbers → number

Key design decisions

• Line-index tracking: parse_key_value_into_map returns the next line index so callers can correctly skip past array bodies in nested structures.
• skip_array_body vs skip_nested_lines: Array bodies containing “- “ list items need special handling to avoid skipping sibling fields at the same indent.
• Auto-detected indent: parse_array_body finds the first “- “ line’s indent rather than assuming base_indent + 2, supporting flexible nesting depths.

Functions

decode

Decode a TOON string back into JSON format.