remove a few redundant phrases

Author: niksirbi

docs/source/project_structure.md

@@ -126,11 +126,13 @@ All filenames follow a key-value pair convention, similar to the [BIDS standard]
 
 ## Label format
 
-* Labels (also referred to as annotations) are only included in the `Train` split, and **must** be stored as JSON files in the same folder as the corresponding frames or clips.
+* Labels (also referred to as annotations) are only included in the `Train` split, and *must* be stored in the same folder as the corresponding frames or clips.
 * Annotations *must* be stored in [COCO keypoints format](https://cocodataset.org/), with some additional requirements described below. Each label file is a JSON file with `images`, `annotations`, and `categories` arrays. Image, annotation and category `id` values *must* be unique integers within a label file.
 
 :::{note}
-Annotation and category `id` values *should* be 1-indexed. This convention follows sleap-io's [`save_coco`](https://io.sleap.ai/latest/reference/sleap_io/io/coco/) function and avoids conflicts with models that treat category `0` as background. Image `id` indexing differs between frame and clip labels — see below for details.
+Annotation and category `id` values *should* be 1-indexed. This convention follows sleap-io's [`save_coco`](https://io.sleap.ai/latest/reference/sleap_io/io/coco/) function and avoids conflicts with models that treat category `0` as background.
+
+Image `id` indexing differs between frame and clip labels — see below for details.
 :::
 
 ### Frame labels (`framelabels.json`)
@@ -159,7 +161,7 @@ Here each `id` is the frame index in the session video (matching the `<frameID>`
 
 ### Clip labels (`cliplabels.json`)
 
-* There *must* be one `cliplabels.json` per clip (in the `Train` split only).
+* There *must* be one `cliplabels.json` per clip.
 * The `images` array *must* contain an entry for every frame in the clip, in consecutive, monotonically increasing order (covering the entire clip duration).
 * Clip labels follow the same COCO keypoints format as frame labels, but with different conventions for image `id` and `file_name` values:
   * Each image `id` *must* be the **0-based index of the frame within the clip** (i.e. `0`, `1`, `2`, ...), not the index in the session video.