docs(chord): slice 6b resume watch cost accepted

packages/chord/docs/next/decisions.md

@@ -1780,7 +1780,9 @@ validation and copies the v2 kernel added around Delta.
   not served here (§7). Stale design text updated: `mapShared` per array, job runs keeping a failed object alive only
   while an attempt is live or activating, `ctx.state.change(fn, ctx)`, revocation closes child links, routes take a
   context, §22's `revoke`/`chain`/`limit`, native watches collapsing only past 100 pending values.
-- **Slice 6b: two numbers accepted (owner, 2026-10-27: "yeah the reopen times are ok"):** reopening a store with
+- **Slice 6b: numbers accepted (owner, 2026-10-27: "yeah the reopen times are ok"; "i accept the 12%": resuming a
+  conversation watch 20 entries back costs about 12% more CPU on `StoreStorage`, once per reconnect, about 0.1 ms per
+  mount, from the extra promise per read in the fork scan):** reopening a store with
   `StoreStorage` costs about 0.15 ms more than `SqliteStorage` once per open (0.28 to 0.43 ms: six table declarations,
   the allocator read, compiling the reads); the one-entry commit's mean is raised by one outlier among 20 samples while
   its p75 is equal or lower. Neither is a hot path or a steady regression. Accepted by the redesign session in fix