Split the stat pass back out of the walk

Phases are strictly sequential again — walk, stat, hash, update per
operand — with parallelism only inside each phase. The walk
enumerates paths with per-directory workers (no lstat of file
entries); the stat pass lstats every collected path with per-file
workers, restoring its exact-total/ETA progress bar and per-file
parallelism inside wide flat directories.

TODO.md

@@ -19,6 +19,12 @@
 
 # Completed Steps
 
+- split the stat pass back out of the walk (2026-07-24, branch
+  `parallel-phases`): phases are strictly sequential again — walk,
+  stat, hash, update per operand — with parallelism only inside each
+  phase; the walk enumerates paths with per-directory workers and the
+  stat pass lstats them with per-file workers, restoring the exact
+  total/ETA stat bar
 - announce each operand on stderr before its passes (2026-07-24,
   branch `scan-operand-progress`): with per-operand walk/hash/update
   cycles, a multi-operand run (e.g. `scan /srv/*`) showed pass totals