docs(runtime): close inventory state ownership

Record J4.2's single Runtime inventory transaction graph, complete Release evidence, exact-binary lifecycle/reconnect acceptance, rollback, and the J4.3 magic/player-sheet boundary. Synchronize architecture, roadmap, milestones, agent guidance, and durable memory.

Co-authored-by: Codex <codex@openai.com>

docs/research/2026-07-26-slice-j4-2-inventory-state.md

@@ -0,0 +1,101 @@
+# Modern runtime J4.2 — inventory transaction ownership
+
+**Status:** COMPLETE
+**Production commit:** `011efbeaa72509b35ea7f4a442e50a2377ae1ea4`
+**Parent plan:** `../plans/2026-07-26-modern-runtime-slice-j4.md`
+
+## Result
+
+`RuntimeInventoryState` is the single presentation-independent owner for the
+live external-container state, item-mana state, shortcut assignments, desired
+spell-component counts, and the retail one-inventory-request-at-a-time
+transaction gate.
+
+It borrows J3's exact `ClientObjectTable`; it does not construct or synchronize
+a second item collection. The live-session router, item interaction,
+retained UI, developer tools, current-runtime/plugin boundary, and future
+no-window hosts all observe those same owner instances.
+
+`InventoryTransactionState` now owns the request/response gate previously
+split across App interaction code. It records the retail request token,
+matches the corresponding response, maintains the shared busy reference,
+tracks use reservations, and resets the transaction atomically. Callback
+failures are isolated after canonical state commits, so one observer cannot
+strand the busy cursor or prevent a later request.
+
+Presentation-only state remains in App: pending backpack-slot projection,
+drag/drop hover and selection, cursor choice, item icons, panel layout, and
+optimistic visual placement. App may borrow the Runtime transaction owner but
+cannot dispose or replace it.
+
+## Retail basis
+
+The ownership move preserves the already-ported retail transaction behavior:
+
+- `ACCWeenieObject::RecordRequest` at `0x0058C220`;
+- `ACCWeenieObject::RecordResponse` at `0x0058CAB0`;
+- `ClientUISystem::UsageCallback` at `0x00565B20`;
+- `2026-07-23-retail-use-busy-ownership-pseudocode.md`;
+- `2026-07-13-retail-give-item-pseudocode.md`.
+
+ACE and Holtburger remain interpretation cross-checks as recorded in the
+busy-ownership pseudocode. No request ordering, wire packet, optimistic move,
+rollback, use-completion, or cursor behavior changed in J4.2.
+
+## Automated evidence
+
+- Runtime suite: 157 passed.
+- App suite: 3,770 passed / 3 established skips.
+- Core suite: 3,305 passed / 2 established skips.
+- Complete Release solution: 8,515 passed / 5 established skips.
+- Release build: pass, zero errors. A clean rebuild reports 17 established
+  test warnings; the J4.2 diff introduces none.
+- `git diff --check`: pass.
+
+The focused matrix covers exact object-table identity, external-container
+open/replace/close, item-mana replacement, shortcut/component replacement,
+request/response matching, use reservations, dispatch failure rollback,
+observer failure isolation, reset/reconnect, borrowed lifetime, idempotent
+disposal, and two independent Runtime instances.
+
+One parallel full-suite run hit the established allocation-sensitive portal
+projection test with a 1,536-byte measurement. The isolated App rerun passed,
+and an immediate complete-solution rerun passed all 8,515 tests without a code
+change.
+
+## Exact-binary connected evidence
+
+`logs/connected-world-gate-20260726-082057/report.json` passed on exact source
+and embedded binary commit
+`011efbeaa72509b35ea7f4a442e50a2377ae1ea4`:
+
+- six capped checkpoints through login, outdoor/dungeon/facility travel and
+  revisit plus one fresh-process uncapped reconnect checkpoint;
+- 244.011-second capped route and 61.422-second reconnect route;
+- both sessions exited gracefully with code zero;
+- zero failures.
+
+Its only warning is the established set of 25 expected world-edge landblock
+misses.
+
+## Divergence audit
+
+J4.2 changes lifetime ownership and failure containment only. It introduces no
+new retail behavior and retires no registered divergence, so the divergence
+register is unchanged.
+
+## Rollback
+
+```text
+git revert 011efbeaa72509b35ea7f4a442e50a2377ae1ea4
+```
+
+Do not revert J3's canonical entity/object ownership to mask an inventory
+transaction failure.
+
+## Next boundary
+
+J4.3 moves construction and lifetime of the coupled `Spellbook` and
+`LocalPlayerState` into Runtime. Immutable DAT spell tables remain supplied by
+the content host; retained spellbook, active-effect, character-sheet, and
+paperdoll presentation remain in App/UI.