Show the walk path on the line below its display (closes #160) (#166)

README.md

@@ -1241,6 +1241,14 @@ On a terminal:
     ⠹ [3/4] hash: [12345/98765], 92 files/s, elapsed 2m32s, remain 17m44s            12% |█         |
     ```
 
+- During `scan`'s `walk`, the line below the display shows the path of the last
+  file the walk found. Each draw shows the path of that moment, cut short before
+  the terminal's last column. The path is escaped as in the reports (see "Report
+  output format"). Each control character left after that is written as `\x` and
+  its code in two hexadecimal digits, such as `\x1b` for the escape character. A
+  control character is one that a terminal acts on instead of showing. The line
+  is erased when the walk ends, and the next phase is drawn on it.
+
 - No line reaches the terminal's last column. A line too wide for the terminal
   first leaves out its rate, the words of a stalled phase, or what the phase is
   waiting for. It leaves out its bar next. It is cut short at the edge only when