Cosmetic: ANSI line wipe; hide (0 packages) on idempotent re-runs

Two nits from YuKu's laptop paste: the 100-space line wipe left a
visible gap before short summaries (now ANSI EL: \r\033[K, no
residue), and '(0 packages)' printed when nothing new was installed
(idempotent re-run / theme deps all present) — the count parenthetical
is now omitted when zero.

lib/common.sh

@@ -173,18 +173,26 @@ ui_quiet_run() {
 
     local rc=0
     wait "$pid" || rc=$?
-    printf '\r%*s\r' 100 '' >&2
+    # ANSI erase-line: wipes the live line without leaving trailing spaces
+    # (a 100-space wipe left a visible gap when the summary was shorter)
+    printf '\r\033[K' >&2
 
     if (( rc == 0 )); then
         n=$(sed -n "$((before+1)),\$p" "$log" 2>/dev/null | grep -ac '^Installing' || true)
-        local plural="s"
-        (( n == 1 )) && plural=""
+        local count_txt=""
+        if (( n > 0 )); then
+            local plural="s"
+            (( n == 1 )) && plural=""
+            count_txt=" (${n} package${plural})"
+        fi
+        # n == 0 means nothing new was installed (idempotent re-run /
+        # deps already present): print the message without a count.
         if (( depth == 256 )); then
-            printf '\033[48;5;34m \033[0m %s (%s package%s)\n' "$msg" "$n" "$plural" >&2
+            printf '\033[48;5;34m \033[0m %s%s\n' "$msg" "$count_txt" >&2
         elif (( depth == 16 )); then
-            printf '\033[42m \033[0m %s (%s package%s)\n' "$msg" "$n" "$plural" >&2
+            printf '\033[42m \033[0m %s%s\n' "$msg" "$count_txt" >&2
         else
-            ok "$msg (${n} package${plural})"
+            ok "$msg${count_txt}"
         fi
         return 0
     else