Establish the standard-library-only Go module and decoder command. The program is a filter: read TOML from **stdin**, write tagged JSON to **stdout**, exit `0`. - **Scalars** — booleans, integers (including `0x`, `0o`, `0b`, underscores), floats (including `inf`, `nan`, exponents), basic and literal strings, then multi-line strings with their line-ending backslash and trimming rules. - **Scalars** — booleans, integers (including `0x`, `0o`, `0b`, underscores), floats (including `inf`, `nan`, exponents), basic and literal strings, then multi-line strings with their line-ending backslash and trimming rules. - **Scaffolding** — line handling, comments, whitespace, the stdin/stdout/exit contract, tagged JSON emission. - **Keys** — bare, quoted, and dotted keys; the redefinition rules. - **Tables** — `[table]`, `[a.b.c]` implicit creation, `[[array of tables]]`, and the rules governing which of these may follow which. - **Inline tables and arrays** — including nesting and the TOML 1.0 restriction that inline tables are closed to later extension. - **Datetimes** — offset, local datetime, local date, local time. - `sh sources/full_test.sh` runs cleanly with zero errors and exits zero.