docs: known issues (perte écriture, réhydratation à froid, écho auto-écriture) + gap 4 sdk-reference

Section 'Known open issues' dans nextgraph-current-state (A ouvert, B indéterminé, C hypothèse-en-cours) + gap 4 (auto-écho non confirmé) dans sdk-reference. Statuts préservés.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014GbGgNEHRejVKoREvFuDFg

packages/client/docs/sdk-reference.md

@@ -244,7 +244,7 @@ helpers live in the consumer app; the SDK exposes the generic reactive/by-need r
 > [`read-model.md`](../../../docs/read-model.md),
 > [`simulation.md`](../../../docs/simulation.md).
 
-Today, on a single shared wallet emulating the mature platform, three gaps diverge
+Today, on a single shared wallet emulating the mature platform, four gaps diverge
 from the reactive contract:
 
 1. **Entity-list reads are one-shot, not reactive.** The reactive ORM cannot be used
@@ -279,5 +279,38 @@ from the reactive contract:
    queryable. At the multi-store migration, opening a repo by cap becomes a native
    broker sync and the anchored read is unchanged.
 
+4. **The subscription may not echo the writer's OWN local commit — HYPOTHESIS
+   (high-confidence), confirmation in progress (2026-07-18); NOT confirmed, NOT
+   fixed.** Unlike gaps 1–3 (designed emulation stopgaps), this is a suspected
+   defect in the polyfill's own reactive assembly. When a client does a local
+   `sparqlUpdate` on a doc it is itself subscribed to (`subscribeDoc` /
+   `ng.doc_subscribe`), the subscription callback appears NOT to fire for its OWN
+   local commit in the same session — so the reactive re-read chain
+   ([`../src/watch-shape.ts`](../src/watch-shape.ts) `watchShape` → `reread` →
+   [`../src/read-model.ts`](../src/read-model.ts) `readUnion`) never runs, and
+   consumers keep the STALE value until the next connection delivers a fresh
+   initial `State`. **Remote** commits DO push correctly (verified: cross-browser
+   reactive update works). A code review verified the consumer wiring is correct,
+   the doc IS in the subscribed set, and a triggered re-read WOULD return the new
+   value — leaving the self-commit echo as the only suspect link. That link is
+   **INFERRED**, not observed: the real `ng.doc_subscribe` runtime is not readable
+   from source, and [`../src/subscribe.ts`](../src/subscribe.ts)'s own doc-comment
+   CLAIMS local writes push a `Patch` — contradicted by the observation. (This
+   also sits in tension with § *The reactivity model* above, which documents the
+   target contract — one commit, every subscriber pushed, local or remote.) The
+   requirement at stake is multi-user: a value change (e.g. a participant count)
+   must propagate reactively to ALL viewers — other viewers (remote push, which
+   works) AND the writer's own view (this suspect link). **Treatment (PLANNED,
+   not done):** confirm first via the temporary instrumentation just added
+   ([`../src/subscribe.ts`](../src/subscribe.ts) ≈`:119` logs
+   `doc_subscribe FIRE <nuri> (State|Patch)`;
+   [`../src/watch-shape.ts`](../src/watch-shape.ts) ≈`:341` logs
+   `reread TRIGGER by <nuri>` — line numbers volatile, grep the log strings);
+   then, IF confirmed, fix **polyfill-side** — a
+   local commit should notify the doc's active `subscribeDoc` callbacks.
+   Consumers must not compensate. Short entry:
+   [`nextgraph-current-state.md`](../../../docs/nextgraph-current-state.md) §
+   *Known open issues*.
+
 When these gaps close, the read path collapses to the reference above: `useShape`
 everywhere, push everywhere, no polling and no re-query-on-signal assembly.