fix(test): isolate uv cache per package to prevent parallel race

Parallel make test targets share a single UV cache directory, causing
rename collisions on macOS (os error 66) when multiple uv processes
write simultaneously.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: raballew

python/.gitignore

@@ -169,4 +169,7 @@ cython_debug/
 
 # Ruff cache
 .ruff_cache/
+
+# Per-package uv cache (parallel test isolation)
+.uv-cache/
 mitmproxy-ca-cert.pem

python/Makefile

@@ -81,7 +81,7 @@ docs-linkcheck: docs-generate-crds docs-generate-grpc
 	uv run --isolated --all-packages --group docs $(MAKE) -C docs linkcheck
 
 pkg-test-%: packages/%
-	uv run --isolated --directory $< pytest || [ $$? -eq 5 ]
+	UV_CACHE_DIR="$(CURDIR)/.uv-cache/$*" uv run --isolated --directory $< pytest || [ $$? -eq 5 ]
 
 pkg-ty-%: packages/%
 	uv run --isolated --directory $< ty check .
@@ -120,6 +120,7 @@ clean-test:
 	-rm -f .coverage
 	-rm -f coverage.xml
 	-rm -rf htmlcov
+	-rm -rf .uv-cache
 
 clean-docs:
 	uv run --isolated --all-packages --group docs $(MAKE) -C docs clean