fix(server): keep short strings whole and typed arrays valid when limiting items

Strings up to 1 KiB are never cut, so a tool call keeps its callId and an
item limits to the same result twice. Arrays drop trailing elements
without inserting a marker element, which typed arrays such as todo items
would reject.

docs/timeline-sync.md

@@ -24,7 +24,10 @@ The invariants are:
 Every item is bounded before it enters either delivery path, because a timeline page is one
 WebSocket message and the daemon closes a socket whose outbound buffer passes 64 MiB. Tool calls get
 64 KiB and other items 256 KiB. Over budget, the largest strings are cut to a shared length with a
-`…[truncated 12.3 MB]` marker, and an oversized `data:` URL is replaced by the marker. The same
+`…[truncated 12.3 MB]` marker, and an oversized `data:` URL is replaced by the marker. Strings up
+to 1 KiB stay whole, so ids and paths survive. Arrays drop their trailing elements without a marker
+element, so typed arrays still match the wire schema. Limiting an item twice gives the same item. The
+budget does not bound wide objects or multi-byte text. The same
 bounded item is used for runtime timeline rows and live stream events. Provider history hydration
 applies the same rule so reopening an agent cannot restore an oversized payload. Fetches apply it
 again to assistant and reasoning rows the projection merges from many chunks.