Deduplicate byte-identical documents (per chunk size)

Collapses source_urls that are byte-identical full documents to a single canonical copy per documents-{N} config, and remaps query gold source_urls to the canonical (gold char spans unchanged). Makes nDCG@10 well defined (only one correct chunk per query).

documents-128/test-00000-of-00001.parquet

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:1913356aa135bc9a5916c8e56f65cdbfbb0e6713d4a44e05b895aabdb211a39a
-size 16697846
+oid sha256:451fbefd08e4664a07057748fb33512eae71735703784b7a0b823fe100060883
+size 5620863

documents-256/test-00000-of-00001.parquet

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:1643a767fda95cf35941c0284bbdbf40ccf63e143792bede1198fe14fe67c601
-size 16098906
+oid sha256:eec68b1d3701a1a07484a9b5f7f535a90b82f540a70ddf29c335593c859d9283
+size 5422169

documents-512/test-00000-of-00001.parquet

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:3726a5be34d927019bc90ba7e1a10e2c11809a2b30ea9cac0e9dd0bfd60bf3af
-size 15836492
+oid sha256:f4f7689778b1e95e3e8da4e9781eb5636c756f26646e60afdfc8ca694236f535
+size 5337248

documents-64/test-00000-of-00001.parquet

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:3a9957ba4b93dfd89d076c682e7b37f9c4c391fdc423eaaefff7cadd2828c601
-size 17640252
+oid sha256:0577ebe3dd5a085282235b83f2c243948a7f18d9855f54f1459b39c5f2086d72
+size 6004414

queries/test-00000-of-00001.parquet

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:521ae81d3fd117c56d86b07d99d69edefc69a29390da4d2ad029d26a93949f4d
-size 5310243
+oid sha256:f1ea13204e9fa9cb01d9ffe4c69cd6e56cf3689c5e7672aa5739b6bdf0fd6718
+size 5310550