feat: verification agent for processor output validation

- New src/verification/ module: verify_output() checks JSON structure/completeness per processor type
- Worker: after processor succeeds, verification agent gates the result
- Passed -> mark completed + cleanup_temp_files (remove .tmp/.partial/.err/timestamp backups)
- Failed -> mark failed with verification details, preserve files for inspection
- cleanup_temp_files() keeps only the canonical {uuid}.{proc}.json

src/lib.rs

@@ -4,6 +4,8 @@ pub mod api;
 
 pub mod ui;
 
+pub mod verification;
+
 pub mod watcher;
 
 pub mod worker;