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

@@ -85,15 +85,15 @@ pkg-test-%: packages/%
 	@mkdir -p $(LOGS_DIR)
 	@rm -f $(LOGS_DIR)/$*.failed
 	@bash -c 'set -o pipefail; \
-	PYTHONUNBUFFERED=1 uv run --isolated --directory $< pytest 2>&1 | tee $(LOGS_DIR)/$*.log; \
+	UV_CACHE_DIR="$(CURDIR)/.uv-cache/$*" PYTHONUNBUFFERED=1 uv run --isolated --directory $< pytest 2>&1 | tee $(LOGS_DIR)/$*.log; \
 	rc=$$?; \
 	if [ $$rc -ne 0 ] && [ $$rc -ne 5 ]; then \
 		touch $(LOGS_DIR)/$*.failed; \
 	fi; \
 	true'
 else
 pkg-test-%: packages/%
-	uv run --isolated --directory $< pytest || [ $$? -eq 5 ]
+	UV_CACHE_DIR="$(CURDIR)/.uv-cache/$*" uv run --isolated --directory $< pytest || [ $$? -eq 5 ]
 endif
 
 pkg-ty-%: packages/%
@@ -147,6 +147,7 @@ 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