feat(weights): record kg or lb, and RiR targets on planned sets

[wromansky]

Three related gaps, all found coaching a real trainee through this server against a self-hosted wger.

1. Everything was kilograms

log_set took weight_kg and never sent weight_unit, so a trainee who trains in pounds had their working weights converted on the way in and back on the way out — 225 lb stored as 102.06 kg — even with their wger profile set to lb. wger models the unit explicitly (/api/v2/setting-weightunit/: 1 = kg, 2 = lb), so there is no reason to flatten it.

log_set, update_workout_log and add_exercise_with_sets now take weight_unit ('kg' or 'lb', default kg), and the number is stored in the unit it was given in.

The parameter is renamed weight_kg → weight, because the name was the bug.

Note the unit lives in two different places in wger, which is easy to miss: a workout log carries its own weight_unit, while a planned set takes it from its slot entry. add_exercise_with_sets sets it on the entry it creates.

2. set_slot_entry_config could not say what a weight meant

Same root cause, worse failure. Setting a planned weight through that tool wrote only the config, leaving the number interpreted in whatever unit the entry already carried.

Observed end to end: an assistant was asked to set a trainee's working weights in pounds, wrote 175 / 50 / 35 / 25 / 40 to five weight configs, and every one landed as kilograms. The plan then read a 175 kg incline barbell press — 386 lb — for five reps. Nothing errored, and the tool's response looked correct.

kind='weight' (and 'max_weight') now accepts weight_unit and patches the entry before writing the config, so one call leaves a coherent record. Passing it with any other kind is refused rather than ignored.

3. A planned set could not carry a RiR target

wger has rir-config for exactly this and the tool ignored it, so autoregulated programming — "3 × 8 leaving 2 in reserve" — could not be expressed in a plan at all, only logged after the fact. add_exercise_with_sets now takes an optional rir.

Related: weight on a planned set is now optional. A coach writing a program for someone whose strength is unknown had to invent a number; omit it and prescribe sets, reps and RiR instead, and let the load be filled in from the first session.

Tests

10 new tests in tests/test_weight_units_and_rir.py: pounds stay pounds, kg remains the default, an unknown unit is refused, a reps-only update leaves the recorded unit untouched, a planned set records both unit and RiR, weight may be omitted, rir stays optional, the unit reaches the entry while the value reaches the config, a unit on a non-weight kind is refused without touching either endpoint, and omitting it leaves the entry alone.

Full suite passes (81) and ruff check is clean.

Note

Touches log_set alongside #3, which extends the same function with routine linkage — they merge cleanly in either order, but whichever lands second will want a trivial rebase. Independent of #2, #4 and #5.