fix(deps): silence polars explode() empty_as_null deprecation warnings

pytest emitted 113 DeprecationWarnings, all from the same source: polars
2.0 changes explode()'s default handling of empty lists from "explode to
null" to "drop the row". Every explode() call site in this repo already
follows the explode with drop_nulls() (or otherwise excludes empty
lists), so the new behavior is what we always wanted — pass
empty_as_null=False explicitly rather than suppressing the warning.

Bump the polars floor from >=1.0 to >=1.43, since the empty_as_null
kwarg doesn't exist before ~1.35.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012dE2r7cNo9Lbthh1JUW1NF

uv.lock

@@ -892,9 +892,9 @@ requires-dist = [
     { name = "pandas", marker = "extra == 'dev'", specifier = ">=2.2,<4" },
     { name = "particle", specifier = ">=1.0,<2" },
     { name = "plotstyle", marker = "extra == 'analysis'", specifier = ">=1.0.0", index = "https://git.larsbogner.de/api/packages/lars/pypi/simple/" },
-    { name = "polars", specifier = ">=1.0,<2" },
-    { name = "polars", marker = "extra == 'analysis'", specifier = ">=1.0,<2" },
-    { name = "polars", marker = "extra == 'convert'", specifier = ">=1.0,<2" },
+    { name = "polars", specifier = ">=1.43,<2" },
+    { name = "polars", marker = "extra == 'analysis'", specifier = ">=1.43,<2" },
+    { name = "polars", marker = "extra == 'convert'", specifier = ">=1.43,<2" },
     { name = "pyarrow", specifier = ">=16,<26" },
     { name = "pytest", marker = "extra == 'dev'", specifier = ">=8,<10" },
     { name = "pytest-cov", marker = "extra == 'dev'", specifier = ">=5,<8" },