Refine tags around physical longitudinal practice

Retain video and computer-vision as routing tags; retain longitudinal-study and drawing-process as the distinctive intersection; remove time-series and self-supervised-learning; add art, time-lapse, analog-media, skill-acquisition, single-creator, and provenance. Clarify that the July 2025 protocol boundary supports era-aware analysis but is not itself a skill-change label.

README.md

@@ -10,11 +10,14 @@ size_categories:
 task_categories:
 - feature-extraction
 tags:
+- video
+- computer-vision
 - art
 - time-lapse
-- analog-drawing
+- analog-media
 - drawing-process
-- longitudinal-archive
+- skill-acquisition
+- longitudinal-study
 - single-creator
 - provenance
 - archival
@@ -179,6 +182,11 @@ describe the published encoded file. Historical canonicalization may include a
 rotation, crop, or transcode; those transformations are documented only where
 evidence currently exists and must not be inferred from dimensions alone.
 
+The July 15, 2025 protocol boundary is explicitly encoded in canonical
+metadata. It supports era-aware comparison of repeated physical-media practice,
+but it is an acquisition change, not a skill-change label. Differences across
+that boundary may reflect capture conditions as well as practice development.
+
 ## Annotation State
 
 The videos are primarily raw and unannotated. The release does not provide:
@@ -198,7 +206,8 @@ source `record_id` and pinned repository revision.
 ### Reasonable uses in the current release
 
 - archival and drawing-process research
-- qualitative within-creator longitudinal analysis over published coverage
+- qualitative within-creator analysis of practice and skill development across
+  repeated physical-media sessions
 - self-supervised video representation experiments
 - frame-change, scene, and workspace analysis
 - development of annotation and tracking methods