Activities guide: both inference request shapes, lift intensity, rest days, brick segments

guides/activities.mdx

@@ -227,13 +227,31 @@ Response:
 
 ```json
 {
+  "activity_type": "run",
   "type": "run",
-  "confidence": 0.95
+  "confidence": 0.95,
+  "request_id": "req_4f2a9c1e7b30"
 }
 ```
 
-`type` is one of the seven activity keys or `"unknown"`. Inference never fails the request: when the model is unavailable or the evidence is too thin, you get `"unknown"` with `confidence: 0`, so branch on the type rather than on an error.
+`activity_type` is one of the seven activity keys or `"unknown"`, and `type` carries the same value. When the model is unavailable or the evidence is too thin, you get `"unknown"` with low or zero confidence rather than an error, so branch on the type. A `502` means the inference service itself could not be reached; it is not counted as usage, so retry with backoff.
 
-Sending more than a title sharpens the result. The endpoint also reads `pre_activity_comment`, `workout_type` (your provider's own coarse type), `velocity` in m/s, `has_power`, and `cadence`, and those structured signals resolve most cases before the model is consulted.
+Sending more than a title sharpens the result. The endpoint also reads `pre_activity_comment`, `workout_type` (your provider's own coarse type), `tss_calculation_method`, `structure_summary`, `velocity` in m/s, `has_power`, and `cadence`, and those structured signals resolve many cases before the model is consulted. The API reference names two of these differently, and both spellings work: `activity_name` is `title`, and `source_type` is `workout_type`. You can also send `device`, the recording device's name.
 
-For multi-sport titles like "Bike/run brick", use `POST /v1/infer/brick-types`. It returns `sub_types` (for example `["bike", "run"]`) with a single `confidence`, and you create one activity per leg.
+A strength session also carries `intensity`: `1` light, `2` medium, `3` heavy. Lift uses levels 1-3 of `intensity_level`, so pass the value unchanged as `intensity_level` when you create the lift activity; rescaling it onto 1-9 raises the carbohydrate ceiling. An entry that marks a day with no training, such as "Rest day", comes back with `"rest_day": true` and type `"unknown"`; it is not a workout to create.
+
+For multi-sport titles like "Bike/run brick", use `POST /v1/infer/brick-types`. It takes the same fields plus an optional `segments` list of the legs you already know, in order, and returns every leg in order:
+
+```json
+{
+  "segments": [
+    {"activity_type": "bike", "order": 1},
+    {"activity_type": "run", "order": 2}
+  ],
+  "sub_types": ["bike", "run"],
+  "confidence": 0.9,
+  "request_id": "req_8d51e0b2c7a4"
+}
+```
+
+`sub_types` is the same list without the order numbers. Create one activity per leg.