-- Duration builtins: dur-parse (text -> R n t) and dur-fmt (n -> t).
-- dur-parse is lenient: accepts abbreviations (s/m/h/d/w), full names
-- (singular + plural), mixed sequences, and decimal quantities.
-- dur-fmt formats seconds as human-readable text; drops zero parts.
-- Parse abbreviated form: "3h 30m" = 12600 seconds.
parse-3h30m>R n t;dur-parse "3h 30m"
-- Parse long form with week and day units.
parse-1w2d>R n t;dur-parse "1 week 2 days"
-- Parse decimal quantity: "1.5 hours" = 5400 seconds.
parse-1pt5h>R n t;dur-parse "1.5 hours"
-- Format 9720 seconds as "2h 42m".
fmt-9720>t;dur-fmt 9720
-- Format exactly one day.
fmt-86400>t;dur-fmt 86400
-- Format 90 seconds as "1m 30s".
fmt-90>t;dur-fmt 90
-- Format zero seconds.
fmt-0>t;dur-fmt 0
-- Round-trip: "2 days 3 hours" parses and re-formats.
roundtrip-2d3h>R t t;n=dur-parse! "2 days 3 hours";~dur-fmt n
-- run: parse-3h30m
-- out: 12600
-- run: parse-1w2d
-- out: 777600
-- run: parse-1pt5h
-- out: 5400
-- run: fmt-9720
-- out: 2h 42m
-- run: fmt-86400
-- out: 1 day
-- run: fmt-90
-- out: 1m 30s
-- run: fmt-0
-- out: 0s
-- run: roundtrip-2d3h
-- out: 2 days 3h