Every `create` timeseries example omits the required `unit` → HTTP 400

[samuelhel]

Summary

The platform requires a non-blank unit on every timeseries at create time, but essentially every "create a series" example in the docs omits it. As written, the create step fails for Java, Python, and Rust — including the quickstart, the first thing a new user runs.

Repro

curl -s -i -X POST "$BASE_URL/timeseries/create" \
  -H "Authorization: Bearer $TOKEN" -H 'Content-Type: application/json' \
  -d '{"items":[{"externalId":"engine_temperature","name":"Engine temperature","valueType":"FLOAT"}]}'
HTTP/1.1 400
{"items":[{"unit":"timeseries.unit.not.blank"}]}
Same failure via the SDK: api.time_series.create_one(&TimeSeries::new("engine_temperature", "Engine temperature")) → 400. Adding a unit (ts.unit = Some("celsius".into())) makes it succeed (201).

Why (not a regression to chase)

The constraint is intentional and long-standing: Timeseries.java carries @NotBlank(message = "timeseries.unit.not.blank") on unit, added in 2024. So the docs must supply a unit — this isn't a platform bug to wait on.

Scope (create sites missing a unit)

- Rust: 2 inline create_one(&TimeSeries::new(...)) — quickstart.mdx (engine_temperature) and discrete.mdx (station_07_scrap).
- Java: ~8 Timeseries.of(...) chains without .unit(...).
- Python: ~38 TimeSeries(external_id=...) without unit= (a few are multi-line false positives; most are real).

Notable cases:
- quickstart.mdx Rust is inconsistent with itself — the Java and Python tabs set unit("celsius"), the Rust tab does not.
- discrete.mdx station_07_scrap is unitless in all three languages.
- Many are legitimately dimensionless (*_fill_pct, *_occupancy_pct, *_moves, *_status, crane_02_hours, loop-created external_id=s) — the platform still requires a non-blank unit for them.

Proposed fix

Add a unit to every create example. Suggested conventions:
- Series whose id encodes a unit: use it (*_pct → "percent", *_kwh → "kWh", *_c → "celsius", *_bar → "bar", *_kpa → "kPa", *_bbl → "bbl", *_ms → "m/s", *_kw → "kW", *_minutes/*_hours → "min"/"h").
- Counts/events (_scrap, _moves, _sales, flagged_payments_feed): "count".
- Status/state (_status): "state".
- Match the language tabs to each other (fix the quickstart Rust to "celsius" first).

Found while running the SDK end-to-end against a live stack (create → ingest → query/aggregate all otherwise work).