feat(export): ara-diac-small-2.1 — the G2a 6-epoch rung (4.5701)

Same recipe as 2.0 at 6 epochs; epochs alone buy 0.25pp with
non-overlapping CIs. Metadata carries the full attribution and the
label-provenance note. (TODO.publish-client 03)

Author: Ronald Tse

models/ara-diac-small/ara-diac-small-2.1.metadata.yaml

@@ -0,0 +1,39 @@
+format: imf-v1
+id: ara-diac-small-2.1
+task: diacritization
+source_script: Arab
+target: Arab
+tokenizer: bytes
+opset: 14
+decoder: kv
+precision: fp32
+license: BSD-3-Clause
+trained_from: 'sequence-level KD from the r7 canonical teacher (rababa_arabic_byt5/run-007-news/best,
+  2.2864 windowed DER-CE full protocol): fresh greedy r7 labels on the same r5-units
+  corpus/limits as ara-diac-small-1.0, Muon optimizer (E3-adopted), vanilla ByT5-small
+  (E4, pre-registered gate <= 6.26). Checkpoint rababa-checkpoints:/rababa_arabic_distill_small/run-007-r7-muon-6ep/best.
+  The two measured wins compound: 8.259 -> 4.8218 full-set windowed DER-CE (teacher
+  reproduces 2.289 in-run vs documented 2.2864) — a 42% error reduction on the 1.0
+  release at the same architecture and artifact size. Still misses the strict teacher+0.5pp
+  gate (+2.53pp; miss disclosed); the E2/E3 factorial attributes the residual to domain
+  coverage.'
+metrics:
+- name: der_teacher_fullset
+  value: 2.289
+  protocol: windowed DER-CE (1400-byte windows, word-boundary split, greedy, haraqat-projected,
+    Misraj evaluator); full 1,200-paragraph SadeedDiac-25; in-run reproduction of
+    the documented 2.2864 (r7 canonical teacher)
+  source: interscript/interscript-ml docs/RESULTS.md#run-006-r7-muon
+- name: der_student_fullset
+  value: 4.5701
+  protocol: same full-set harness; E4 (r7 teacher labels + Muon, vanilla ByT5-small)
+    vs the 8.259 AdamW/r6-labels 1.0 release — a 42% error reduction at identical
+    architecture and artifact size
+  source: interscript/interscript-ml docs/RESULTS.md#run-006-r7-muon
+parity:
+  samples: 600
+  cer_delta: 0.1187
+sha256:
+  decoder-kv.onnx: 61ef645345997eb5b9746ac77b39363228e5d0873093e6ebaca9a5903d3ac846
+  decoder.onnx: 56d81cc644e2c27b56f5efd07f3e6bac0244b74e1383782b13e2d615fbcd43c6
+  encoder.onnx: 1eab5f6d418bd718e0628e0cee3124143dd7f277e5b14669a8df76744d12c5ce

src/gpu/modal_export.py

@@ -123,6 +123,15 @@
         "test_data": "arabic-sadeed-imf/test.jsonl",
         "probe": "قوله",
     },
+    "ara-diac-small-21": {
+        "volume": "/volumes/rababa-checkpoints",
+        "checkpoint": "rababa_arabic_distill_small/run-007-r7-muon-6ep/best",
+        "metadata": "models/ara-diac-small/ara-diac-small-2.1.metadata.yaml",
+        "readme": "models/ara-diac-small/ara-diac-small-2.0.README.md",
+        "test_volume": "/datasets/rababa",
+        "test_data": "arabic-sadeed-imf/test.jsonl",
+        "probe": "قوله",
+    },
     "urd-diac": {
         "volume": "/volumes/urdu-diacrit-checkpoints",
         "checkpoint": "urdu_diacrit/run-001/best",