test(02-01): add failing tests for INF parser

- 11 test functions covering all DRV-02 and DRV-05 behaviors
- _detect_encoding tests for UTF-16 LE, UTF-16 BE, UTF-8 BOM, ANSI/cp1252
- parse_inf tests: literal DriverDesc, %TOKEN% resolution, UTF-16 fixture
- Multi-model deduplication, architecture detection (x64/arm64/x86/mixed)
- .cat file detection, unused files detection, empty models section
- INF fixtures: sample.inf, sample_utf16.inf (UTF-16 LE BOM), sample_multi_model.inf
- imptune/services/__init__.py package marker

tests/fixtures/sample.inf

@@ -0,0 +1,14 @@
+[Version]
+Signature="$Windows NT$"
+Class=Printer
+Provider=%MFG%
+
+[Manufacturer]
+%MFG%=Models,NTamd64
+
+[Models.NTamd64]
+%DRIVER_NAME%=Install,{12345678-1234-1234-1234-123456789012}
+
+[Strings]
+MFG="Test Manufacturer"
+DRIVER_NAME="Test LaserJet Pro"