fix(proguard): Address PR feedback

- Use exhaustive match instead of wildcard in is_usable() and
  get_problem() to catch future DifFile variants at compile time
- Add test verifying UUID generation succeeds for mappings without
  line info

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: romtsn

src/utils/dif.rs

@@ -380,7 +380,7 @@ impl<'a> DifFile<'a> {
     pub fn is_usable(&self) -> bool {
         match self {
             DifFile::Archive(_) => self.has_ids() && self.features().has_some(),
-            _ => true,
+            DifFile::Proguard(..) => true,
         }
     }
 
@@ -391,7 +391,7 @@ impl<'a> DifFile<'a> {
             } else {
                 "missing debug or unwind information"
             }),
-            _ => None,
+            DifFile::Archive(..) | DifFile::Proguard(..) => None,
         }
     }
 

tests/integration/_cases/proguard/proguard-uuid-no-line-info.trycmd

@@ -0,0 +1,6 @@
+```
+$ sentry-cli proguard uuid tests/integration/_fixtures/proguard.txt
+? success
+5db7294d-87fc-5726-a5c0-4a90679657a5
+
+```