RESULT: FAILED

FILES CHANGED:
- cmd/toml-decoder/main.go
- cmd/toml-decoder/main_test.go
- internal/toml/toml.go

SUMMARY:
Implemented and verified the decoder stdin, tagged-JSON, stderr diagnostic, and exit-status contract. Decoder and architecture gates pass. Full conformance fails on parser features assigned to later stages.

BLOCKERS:
- Full suite remains failing: 167 valid and 59 invalid cases failed.

FAILURE_SUMMARY: Full TOML conformance is incomplete
FAILURE_DETAIL: The current parser only supports basic scalar key/value pairs; later parser stages must implement arrays, tables, floats, datetimes, and strict validation before rerunning the full suite.