* fix(chat): preserve tool duration across session switches Fix #1636: ToolPart.tsx reset pinnedTime to empty on unmount/remount, causing LiveDuration to not render on first paint. Now initializes pinnedTime from server-provided time?.start/time?.end in the useState initializer, eliminating the one-frame gap. * fix(sync): preserve tool state.time in materialization merge --------- Co-authored-by: Leonid Skorobogatyy <bash@opencode.itc.local>