T9.2 - CR-017: Actual Hours is still there, still optional, still counted

A guard, not a build. Removal was floated in the meeting and rejected -
Marlena tracks actual hours so they can be measured - and CLAUDE.md carries
that as a recorded decision. Verified after eight waves of change:

- Actual Hours exists in Closeout (wp_actual_hrs), persists through collect,
  and prints on the export
- it is OPTIONAL: a package closes with it empty (driven, not assumed)
- it rolls up per T6.4: rollup_check has pinned actual-hours aggregation at
  every level since wave 6, and /api/wps/metrics carries actual_hours in its
  buckets

The follow-up the done-when requires is logged as BL-023: a productivity
factor (actual / estimated) - the rollup endpoints already carry both sums,
so it is a presentation task awaiting its own item id and a placement call.

Verification: export_check.py extended to 20/20 (the CR-017 section).

Items: CR-017

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/waves/backlog.md

@@ -493,3 +493,17 @@ deliberately deferred.
   change, criterion satisfied as written) or name the chrome to compress and it
   becomes a small T9 task. The strict check stays red so the question cannot be
   forgotten.
+
+### BL-023 — Productivity factor: actual against estimated hours
+
+- **Found during:** T9.2 (logged as that task's done-when requires)
+- **Where:** future — dashboard / rollups
+- **What:** Actual Hours is tracked (CR-017, deliberately kept) and estimated
+  hours exist on every package; nothing yet compares them. A productivity
+  factor (actual ÷ estimated, rolled up by discipline / building / type the way
+  CR-018 rolls cost) is the measurement Marlena's tracking exists to enable.
+  The rollup endpoints (`/api/wps/metrics`, `/api/projects/{id}/summary`)
+  already carry both sums, so this is a presentation task, not a data one.
+- **Why not now:** new scope — needs its own item id per the working rules, and
+  a product conversation about where it displays and who reads it.
+- **Suggested wave or follow-up:** next revision; needs Nick for placement.