Where an effective setting’s value came from (§8.3’s precedence order,
highest first): an explicit flag, a real environment variable, a local
.env file, a global .env file, or the tool’s built-in default.
Output format (§6.5, §11.2, §11.3). Text is the default, human-readable
floor; Json emits the protocol’s own response types, one document or
JSONL depending on --stream.
Parse args the same way the real binary parses std::env::args_os(), then
run the resulting command. Kept separate from run because recovering
the interleaved order of send’s repeatable part flags
(--text-part/--file-part/--data-part/--media-type) needs the raw
ArgMatches, which Cli::parse() alone discards.