Update README for canonical collection structure

Document Standard_Time_Lapses as the 303-record canonical collection and add Pre_Standard_Time_Lapses as a separate historical collection.

README.md

@@ -14,11 +14,13 @@ tags:
 
 **A 14-Year Longitudinal Archive of Analog Drawing Process (2012–Present)**
 
-## Canonical collection and legacy sources
+## Canonical collection and historical sources
 
-The **303 root-level MP4 files** are the canonical dataset records. Use [`metadata.csv`](metadata.csv) as the machine-readable index; it contains exactly one verified row for every root-level MP4.
+The 303 MP4 files in `Standard_Time_Lapses/` are the canonical dataset records. Use `metadata.csv` as the machine-readable index; it contains exactly one verified row for every canonical MP4.
 
-`Series_9x12/` is retained as a legacy source collection for reproducibility and provenance. It contains historical source files, aliases, and alternate encodes and should not be treated as the canonical file set. Do not infer root-to-legacy relationships from filenames alone.
+`Pre_Standard_Time_Lapses/` contains earlier time-lapse recordings that predate the standard acquisition specifications. It is maintained as a separate collection with its own `metadata.csv` and `SCHEMA.md`.
+
+`Series_9x12/` is retained as a legacy source collection for reproducibility and provenance. It contains historical source files, aliases, and alternate encodes and should not be treated as the canonical file set. Do not infer canonical-to-legacy relationships from filenames alone.
 
 The completed [2026-07-31 provenance release](Provenance_Releases/2026-07-31/) documents the verified relationships. The directly browsable [`consolidated_map.csv`](Provenance_Releases/2026-07-31/consolidated_map.csv) records all 303 determinations; the release ZIP contains the formatted workbook and supporting audit tables.