report,ui: name the tee log by flow kind

BuildTarget::source_only carried two states for what is a three-way
distinction now that pkh test exists: replace it with a TargetKind
(Source/Binary/Test) and derive the tee log prefix (build-/deb-/test-)
from it, so test runs get their own log family instead of borrowing
the deb one.

src/deb/mod.rs

@@ -12,7 +12,7 @@ use crate::logfmt::{
     AptInstallClassifier, AptUpdateClassifier, Classifier, GenericClassifier, MakeClassifier,
     MmdebstrapClassifier, QuiltClassifier,
 };
-use crate::report::{BuildTarget, BuildView};
+use crate::report::{BuildTarget, BuildView, TargetKind};
 use std::error::Error;
 use std::path::{Path, PathBuf};
 use std::sync::Arc;
@@ -256,7 +256,7 @@ async fn build_binary_package_impl(
         version: &version,
         target: &format!("{series}/{arch}"),
         display: format!("Building {package} ({version}) for {series}/{arch}"),
-        source_only: false,
+        kind: TargetKind::Binary,
         tee_log: true,
     });