fix: use ID-based lookup for parallel tool finalization

Replaces map-based index tracking with direct ID lookup when finalizing
streaming tool calls. This prevents duplicate rendering of parallel tools
by ensuring idempotent processing.

Changes:
- Use findIndex with partial===true check instead of streamingToolCallIndices
- Skip already-finalized tools to eliminate race conditions
- Works for both sequential and parallel tool calling modes

The previous approach relied on streamingToolCallIndices map which could
become stale when multiple code paths (finalization loop, sweep fix,
pending updates) process the same tool, causing duplicate rendering.

Author: daniel-lxs

src/core/task/Task.ts

@@ -3240,17 +3240,28 @@ export class Task extends EventEmitter<TaskEvents> implements TaskLike {
 						// Finalize the streaming tool call
 						const finalToolUse = NativeToolCallParser.finalizeStreamingToolCall(event.id)
 
-						// Get the index for this tool call
-						const toolUseIndex = this.streamingToolCallIndices.get(event.id)
+						// Find by ID, not tracked index - can't get stale
+						// Only match partial blocks to ensure idempotent processing
+						// If a tool was already finalized (partial === false), skip it
+						const toolIndex = this.assistantMessageContent.findIndex(
+							(block) =>
+								(block.type === "tool_use" || block.type === "mcp_tool_use") &&
+								(block as any).id === event.id &&
+								block.partial === true,
+						)
+
+						if (toolIndex === -1) {
+							// Already finalized - clean up tracking and skip
+							this.streamingToolCallIndices.delete(event.id)
+							continue
+						}
 
 						if (finalToolUse) {
 							// Store the tool call ID
 							;(finalToolUse as any).id = event.id
 
-							// Get the index and replace partial with final
-							if (toolUseIndex !== undefined) {
-								this.assistantMessageContent[toolUseIndex] = finalToolUse
-							}
+							// Replace partial with final
+							this.assistantMessageContent[toolIndex] = finalToolUse
 
 							// Clean up tracking
 							this.streamingToolCallIndices.delete(event.id)
@@ -3260,11 +3271,11 @@ export class Task extends EventEmitter<TaskEvents> implements TaskLike {
 
 							// Present the finalized tool call
 							presentAssistantMessage(this)
-						} else if (toolUseIndex !== undefined) {
+						} else {
 							// finalizeStreamingToolCall returned null (malformed JSON or missing args)
 							// We still need to mark the tool as non-partial so it gets executed
 							// The tool's validation will catch any missing required parameters
-							const existingToolUse = this.assistantMessageContent[toolUseIndex]
+							const existingToolUse = this.assistantMessageContent[toolIndex]
 							if (existingToolUse && existingToolUse.type === "tool_use") {
 								existingToolUse.partial = false
 								// Ensure it has the ID for native protocol