chore(python): upgrade eval fixture dependencies

Move the Python eval fixture to Python 3.14 and refresh its uv lockfile
with newer autoevals and braintrust releases. Remove the unused root uv
lockfile so Python fixture dependency state stays scoped to test-eval-py.

Author: AbhiPrasad

.python-version

@@ -1 +1 @@
-3.12
+3.14

mise.toml

@@ -1,4 +1,4 @@
 [tools]
 nodejs = "24.15.0"
 pnpm = "10.33.0"
-python = "latest"
+python = "3.14"

test-eval-py/.python-version

@@ -1 +1 @@
-3.12
+3.14

test-eval-py/pyproject.toml

@@ -3,5 +3,8 @@ name = "test-eval-py"
 version = "0.1.0"
 description = "Add your description here"
 readme = "README.md"
-requires-python = ">=3.12"
-dependencies = ["autoevals>=0.0.92", "braintrust>=0.0.160"]
+requires-python = ">=3.14"
+dependencies = [
+    "autoevals>=0.3.0",
+    "braintrust>=0.26.0",
+]