D12 - the productivity factor, on the dashboard (was BL-023)

Nick's decision: 'find a spot on the dashboard.' The spot: an eighth metric
card beside Est./Actual hrs - actual/estimated to two decimals, green at or
under 1.0, red over. Both hour fields are optional (CR-017), so with nothing
to divide the card shows an em dash rather than vanishing: a metric that
disappears reads as 'no such measure', not 'nothing logged yet'. Server sums
(B4), the same m.est_hours/actual_hours its neighbours already render - zero
new fetches, and the card stays inside the block the metrics-failure path
skips, so an outage still shows the error panel and no cards.

aggregates_check gains the pin (16 -> 17): the card must equal the quotient
of the SERVER's sums, or the em dash when either sum is zero - derived, not
hardcoded. Backlog entry corrected in passing where it credited
/api/projects/{id}/summary with hour sums it never carried.

Items: D12 (decisions-2026-08-20.md), CR-017 read, B4 discipline.

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

docs/waves/backlog.md

@@ -518,8 +518,9 @@ deliberately deferred.
   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.
+  `/api/wps/metrics` already carries both sums, so this is a presentation
+  task, not a data one. (Corrected at D12: the entry originally credited
+  `/api/projects/{id}/summary` too, which carries no hours at all.)
 - **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.