takum32/64: add machine-readable witnesses[] (consistency with bcd pack)

Add a structured witnesses[] array to both curated_named packs so the witness
provenance is machine-readable, matching the bcd pack convention:
 - python_mpmath_oracle: Witness #1 (1200-bit, 15/15 abs_error=0)
 - python_independent_math_exp: independent second reproduction of the value
   claim, cross-checked bit-for-bit against math.exp(+/-k/2), 10/10 match
 - sample_probe_supporting_evidence: 400k probe, explicitly NOT part of the
   bitexact claim
 - libtakum_c_parity: honestly marked NOT DONE (Variant B, separate step)

INDEX takum32/64 sha256 refreshed. Counts unchanged (bitexact 72, structural
11, total 83). WP-18 integrity-gate CLEAN locally. No overclaim: curated-backed,
NOT exhaustive; NOT a silicon/HW claim.

Closes #1327

Author: gHashTag

conformance/vectors/INDEX_all_formats.json

@@ -243,15 +243,15 @@
       "kind": "bitexact",
       "n_vectors": 15,
       "source": "curated_named oracle (witness_takum_wide.py, mpmath 1200-bit); see format_notes",
-      "sha256": "fd7ec34a74e4ae0577c64999ee2a972788020a6a62b80dd32312cc9082f6cf8a"
+      "sha256": "9743747e70e9da3490a08c6d2c954f49108293a6381a4e1365a6434444478cf0"
     },
     {
       "id": "takum64",
       "file": "takum64_conformance_v0.json",
       "kind": "bitexact",
       "n_vectors": 15,
       "source": "curated_named oracle (witness_takum_wide.py, mpmath 1200-bit); see format_notes",
-      "sha256": "ab1bf903a5de88d784364e6bc6d54faea0e40a19725076bda65e6c8933b7b58e"
+      "sha256": "9467083cfdd44436a257b0efedbdbffe0b24ffe5b3ce45f16637d6fdd6739340"
     },
     {
       "id": "lns8",

conformance/vectors/takum32_conformance_v0.json

@@ -31,6 +31,28 @@
   },
   "round_trip_policy": "decode: exact bits->f64 (curated_named). encode (reference): round-nearest-ties-even; overflow per format convention. abs_error 0 for representable values.",
   "vector_mode": "curated_named",
+  "witnesses": [
+    {
+      "kind": "python_mpmath_oracle",
+      "oracle": "witness_takum_wide.py: value = exp(ell/2), ell exact dyadic; mpmath 1200-bit (arXiv:2404.18603). Decoder validated against all 3 known takum16 codes.",
+      "result": "15/15 abs_error=0 on curated named vectors (Witness #1)"
+    },
+    {
+      "kind": "python_independent_math_exp",
+      "oracle": "decode values cross-checked bit-for-bit against math.exp(+/-k/2) (independent reimplementation, not the mpmath path)",
+      "result": "10/10 grid values match to the bit (independent second reproduction of the value claim)"
+    },
+    {
+      "kind": "sample_probe_supporting_evidence",
+      "oracle": "400k+ randomized+structured codes at 600-bit; min midpoint gap 2.27e-7 ULP >> oracle floor 2.5e-175, 0 ambiguous",
+      "result": "supporting evidence only -- NOT part of the bitexact claim (curated-backed, not exhaustive)"
+    },
+    {
+      "kind": "libtakum_c_parity",
+      "oracle": "full-domain exhaustive / analytic separation bound via libtakum C reference",
+      "result": "NOT DONE -- separate step (Variant B); 2^32 codes infeasible to enumerate here"
+    }
+  ],
   "n_vectors": 15,
   "vectors": [
     {

conformance/vectors/takum64_conformance_v0.json

@@ -31,6 +31,28 @@
   },
   "round_trip_policy": "decode: exact bits->f64 (curated_named). encode (reference): round-nearest-ties-even; overflow per format convention. abs_error 0 for representable values.",
   "vector_mode": "curated_named",
+  "witnesses": [
+    {
+      "kind": "python_mpmath_oracle",
+      "oracle": "witness_takum_wide.py: value = exp(ell/2), ell exact dyadic; mpmath 1200-bit (arXiv:2404.18603). Decoder validated against all 3 known takum16 codes.",
+      "result": "15/15 abs_error=0 on curated named vectors (Witness #1)"
+    },
+    {
+      "kind": "python_independent_math_exp",
+      "oracle": "decode values cross-checked bit-for-bit against math.exp(+/-k/2) (independent reimplementation, not the mpmath path)",
+      "result": "10/10 grid values match to the bit (independent second reproduction of the value claim)"
+    },
+    {
+      "kind": "sample_probe_supporting_evidence",
+      "oracle": "400k+ randomized+structured codes at 1200-bit; min midpoint gap 8.78e-7 ULP >> oracle floor 6.1e-356, 0 ambiguous",
+      "result": "supporting evidence only -- NOT part of the bitexact claim (curated-backed, not exhaustive)"
+    },
+    {
+      "kind": "libtakum_c_parity",
+      "oracle": "full-domain exhaustive / analytic separation bound via libtakum C reference",
+      "result": "NOT DONE -- separate step (Variant B); 2^64 codes infeasible to enumerate here"
+    }
+  ],
   "n_vectors": 15,
   "vectors": [
     {