Add siglip-base-patch16-224 and mistral-7b-v0.1 oracle fixtures

tk-convert's tests/oracle.rs (huggingface/tokenizers) and the Makefile's ORACLE_RESOURCES already reference fixtures/models/siglip-base-patch16-224.json and fixtures/models/mistral-7b-v0.1.json, but neither file was ever pushed here -- both tests fail loudly on a fresh checkout. Adding the two tokenizer.json files straight from google/siglip-base-patch16-224 and mistralai/Mistral-7B-v0.1.

fixtures/models/mistral-7b-v0.1.json

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:11c08db21487c885d8c792180f0be237f6a261b89a46f128a6a80a3aa4bd1720
+size 1795188

fixtures/models/siglip-base-patch16-224.json

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:c6e405cb7c670d56636a9402c81023a55bc6c3c53d89cf02b92f5c5005bfe920
+size 2399357