fix(streaming_renderer): better way to shift part lines

Rather than iterating over the entire part cache, start from the most
recent part in the most recent message and stop when it's lines are
earlier than the change

Author: cameronr

lua/opencode/ui/streaming_renderer.lua

@@ -75,16 +75,34 @@ function M._shift_lines(from_line, delta)
     return
   end
 
-  vim.notify('Shifting lines from: ' .. from_line .. ' by delta: ' .. delta)
+  local examined = 0
+  local shifted = 0
 
-  for part_id, part_data in pairs(M._part_cache) do
-    if part_data.line_start and part_data.line_start >= from_line then
-      part_data.line_start = part_data.line_start + delta
-      if part_data.line_end then
-        part_data.line_end = part_data.line_end + delta
+  for i = #state.messages, 1, -1 do
+    local msg_wrapper = state.messages[i]
+    if msg_wrapper.parts then
+      for j = #msg_wrapper.parts, 1, -1 do
+        local part = msg_wrapper.parts[j]
+        if part.id then
+          local part_data = M._part_cache[part.id]
+          if part_data and part_data.line_start then
+            examined = examined + 1
+            if part_data.line_start < from_line then
+              -- vim.notify('Shifting lines from: ' .. from_line .. ' by delta: ' .. delta .. ' examined: ' .. examined .. ' shifted: ' .. shifted)
+              return
+            end
+            part_data.line_start = part_data.line_start + delta
+            if part_data.line_end then
+              part_data.line_end = part_data.line_end + delta
+            end
+            shifted = shifted + 1
+          end
+        end
       end
     end
   end
+
+  -- vim.notify('Shifting lines from: ' .. from_line .. ' by delta: ' .. delta .. ' examined: ' .. examined .. ' shifted: ' .. shifted)
 end
 
 function M._apply_extmarks(buf, line_offset, extmarks)