The count defect was two things; only the one that is not ours is left

`bug_participant-count-stays-at-zero` described a failure that no longer exists
and an open question that turned out to be the same failure seen from the other
side. It becomes `caveat_participant-count-one-connection-lag`, and the type
change is the point: what remains is a bounded delay whose cause sits entirely
outside the application, not a defect this repo can act on.

Gone from it: the multi-inbox race, "never converges", and the withdrawal
asymmetry recorded as unexplained. That asymmetry WAS the race — with one inbox
per document both paths now share the identical one-connection lag, so nothing
is left unaccounted for.

What it says now: the count needs one connection more than the write that
produced it, because the layer does not notify you of your own actions — a
deposit into an inbox you watch raises no push, and a write to your own document
is not re-read in the writing session. Both measured, both raised with the
provider, and neither compensated here: a retry or a poll is precisely what the
doctrine forbids.

Repaired alongside: the leaves that still described DELETE-then-INSERT, the
materializer's old shape, and the probe cookbook's tally of open defects. The
two new primitives are recorded where the shared utilities are listed, marked
unit-tested.

.project/concepts/app-architecture/_debt.md

@@ -1,7 +0,0 @@
-# Doc-debt — app-architecture
-
-> Presence of a block = doc to update. Processed → delete the block; no blocks left → delete this file.
-> One block = one "big change": `why` + `files` + `verify` (leaves to review).
-
-## Raw markers (consolidate into blocks, then delete)
-- TOUCHED src/shared/context/FestipodDataContext.tsx @2026-08-16 (session 0b064e8b-1717-421f-a20e-a4318ad217b1)

.project/concepts/app-architecture/knowledge_module-structure.md

@@ -34,7 +34,7 @@ Each module may contain:
 | `data/` | User stories, `features.ts` (auto-generated), `seedData.ts`, `types.ts` |
 | `hooks/` | empty — the reactive read binding lives in `data/useShapeQuery.ts` (concept `data-layer`) |
 | `shapes/` | SHEX + ORM bindings (see concept `data-layer`) |
-| `utils/` | `ngSession.ts`, `ngBootstrap.ts`, `ngGraph.ts`, `storeRegistry.ts`, `connections.ts`, `identifier.ts` |
+| `utils/` | `ngSession.ts`, `ngBootstrap.ts`, `ngGraph.ts`, `storeRegistry.ts`, `connections.ts`, `identifier.ts`, `resolveOnce.ts` (single-flight resolution per key, unit-tested), `serialTask.ts` (a task that never runs concurrently with itself, unit-tested) |
 | `steps/`, `support/` | Shared Cucumber step definitions and hooks (concept `bdd-testing`) |
 | `lib/` | Helpers (`cn`, etc.) |