deb: give the build-user setup and resume cleanup their own phases

The profile's build-dependency phase spanned everything between the
apt passes and the build step, and for a kernel incremental build
that hid ~13 minutes of housekeeping: the recursive chown handing
the staged tree to the build user, and the resume_clear quirk
dropping the previous attempt's stamp caches. Both now enter the
profiler (ClearingResumeCaches only when the quirk has paths and a
tree is carried, PreparingBuildUser only for rootless builds), so
the status bar and pkh deb profile show where the time actually
goes — on a large carried tree the chown dominates, which is the
honest answer to a 6m30s DEPS column next to a 19m19s phase.

src/deb/local.rs

@@ -639,8 +639,10 @@ pub async fn build(
     // with no config prerequisite) would build from the previous
     // attempt's configuration: drop the listed caches so the wrapper
     // steps re-run over the incremental inner builds.
-    if build_resume {
-        for rel in crate::quirks::get_resume_clear_paths(package, series) {
+    let resume_clear_paths = crate::quirks::get_resume_clear_paths(package, series);
+    if build_resume && !resume_clear_paths.is_empty() {
+        enter_phase(view, Phase::ClearingResumeCaches, profiler);
+        for rel in resume_clear_paths {
             let path = Path::new(package_dir_str).join(&rel);
             if !ctx.exists(&path).unwrap_or(false) {
                 continue;
@@ -689,7 +691,12 @@ pub async fn build(
     // LTO/make -j process flood), and a rules chown that fails for the
     // build user is cosmetic — the .deb is assembled in the binary step's
     // own fakeroot session, where files unknown to its database are
-    // recorded as root-owned anyway.
+    // recorded as root-owned anyway. Handing the tree over is a recursive
+    // chown that can take minutes on a large carried tree, so it is a
+    // phase of its own in the status bar and the profile.
+    if build_user.is_some() {
+        enter_phase(view, Phase::PreparingBuildUser, profiler);
+    }
     let rule_ids = match build_user {
         Some(_) => {
             let workroot = Path::new(package_dir_str)