Keep each walk's phases and say a delivery over its budget (hq ADR 0282 slice 1, issue 382)

The operator's budget (a leaf module running everywhere within five minutes
of its merge, a core module within ten) cannot be held to without knowing
where a walk's time goes. A walk now keeps when its batch's window closed,
when it was cut and its class (migration 0093), each gate reading, and what
each machine of the rest was sent; 'delivery walks' and plan-moved say its
phases from the merge to every machine of the rest reporting the build
applied, and ended walks keep them as walk-phase durations per class. Probe
D16 reads mesh-delivery's 'times' and raises delivery.<class>.over-budget.
A phase that cannot be measured is said unknown, never zero. Measurement
only: no walk is held, sent or judged differently.

internal/inventory/migrations/0093-a-walk-keeps-its-phases.sql

@@ -0,0 +1,10 @@
+-- A walk keeps its phases (novox/hq ADR 0282 decision 6, issue 382).
+--
+-- A small fix took 45 minutes to reach a node on 2026-10-10, and where the time went was read back from the
+-- walks by hand: the walk kept when its modules were asked, built, sent first, judged and sent to the rest,
+-- but not when its batch's window closed or when it was cut, so the window and the wait behind another walk
+-- could not be told apart. A walk now keeps those moments and its class (core or leaf, read at its cut).
+-- Its readings, each module's send to the rest and the times of the merges it answers are kept in the plan's
+-- own records (modules, delivery). Null for a walk kept before this: its phases before the build are said
+-- unknown.
+alter table release_plan add column times jsonb;