lib.PackageFilter: Add unit tests

PackageFilterString is pure regex logic without test coverage.

Add unit tests for the url=~ filter, packages without a url, whitespace
around the operator, and the rejection of unsupported filter definitions.

Signed-off-by: Jan Lindemann <jan@janware.com>
Assisted-by: unsloth/Qwen3.8-27B-GGUF:Q4_K_M with pi.dev v0.85.1

test/unit/python/jw/pkg/lib/PackageFilter/Makefile

@@ -0,0 +1,7 @@
+TOPDIR = ../../../../../../..
+
+include $(TOPDIR)/make/proj.mk
+include $(JWBDIR)/make/py-run.mk
+
+all:
+test: run

test/unit/python/jw/pkg/lib/PackageFilter/test.py

@@ -0,0 +1,34 @@
+from jw.pkg.lib.Package import Package
+from jw.pkg.lib.PackageFilter import PackageFilterString
+
+pkg = Package(name = 'jw-core', url = 'https://example.com/jw-core')
+pkg_other = Package(name = 'jw-base', url = 'https://other.org/jw-base')
+pkg_nourl = Package(name = 'no-url')
+
+# -- url=~ filters --
+
+f = PackageFilterString('url=~example\\.com')
+assert f.match(pkg)
+assert not f.match(pkg_other)
+# A package without a url never matches
+assert not f.match(pkg_nourl)
+
+# Whitespace around the operator is tolerated
+f = PackageFilterString('  url  =~  example')
+assert f.match(pkg)
+
+# An unanchored regex matches anywhere in the url
+f = PackageFilterString('url=~jw-core$')
+assert f.match(pkg)
+assert not f.match(pkg_other)
+
+# -- Unsupported definitions raise --
+
+for definition in ('', 'url=example.com', 'name=jw-core', 'url ~ example'):
+    try:
+        PackageFilterString(definition)
+        assert False, f'Should have raised for "{definition}"'
+    except Exception:
+        pass
+
+print('All PackageFilter tests passed')