## Why
Inferring wait targets from request arguments can abort trace replay on malformed arguments and link waits to cells the host never resolved.
## What changed
Record an explicit `CodeCellWaitTargetResolved` event when the host confirms a live cell, and expose its runtime handle as `resolved_wait_runtime_cell_id` on the tool call. Build cell wait links from these observations, preserving links while cell source is pending and preventing late confirmations from linking to recycled handles after thread resume.
Older traces no longer infer wait links from request arguments, so an empty `wait_tool_call_ids` list does not establish that nobody waited on a cell.
## Testing
Extend dispatch and replay tests to cover live, missing, and invalid wait targets, pending cell source, legacy traces, and runtime handle reuse across threads and resume.
GitOrigin-RevId: 0f13b291c197c5487258b6ce36276cf1f19e2b6d
tongzhou wang
9d12d007b2