feat(chat): stream partial tool output during live agent response

Live tool calls that produce output while running (e.g. streaming bash
stdout from Codex) now render their partial output in real time instead
of appearing blank until the tool completes. The tool card keeps its
running visual state — spinner and 24KB tail truncation — while chunks
arrive, and transitions to the completed state once the final status
lands. A WeakMap keyed on the ACP reducer's chunks-array identity
memoizes the joined output so repeated renders don't re-run O(n) string
concatenation.

src/lib/adapters/ai-elements-adapter.ts

@@ -600,11 +600,19 @@ function buildToolResultMap(
 /**
  * Transform a MessageTurn (from backend) to AdaptedMessage format.
  * Same correlation logic as adaptUnifiedMessage but operates on turn.blocks.
+ *
+ * `inProgressToolCallIds` lets streaming consumers expose partial tool output
+ * (e.g. terminal stdout streamed during execution) without flipping the tool
+ * into a "completed" visual state. When a tool_use's id is in this set, the
+ * adapter emits state="input-available" with the partial output attached, so
+ * the renderer can keep showing the running spinner while the live output
+ * streams in.
  */
 export function adaptMessageTurn(
   turn: MessageTurn,
   text: AdapterMessageText,
-  isStreaming: boolean = false
+  isStreaming: boolean = false,
+  inProgressToolCallIds?: Set<string>
 ): AdaptedMessage {
   const adaptedContent: AdaptedContentPart[] = []
   const resultMap = buildToolResultMap(turn.blocks)
@@ -635,6 +643,9 @@ export function adaptMessageTurn(
         ? resultMap.get(block.tool_use_id)
         : undefined
 
+      const isToolStillRunning =
+        !!block.tool_use_id && !!inProgressToolCallIds?.has(block.tool_use_id)
+
       if (matchedResult) {
         matchedResultIds.add(block.tool_use_id!)
         adaptedContent.push({
@@ -642,7 +653,11 @@ export function adaptMessageTurn(
           toolCallId,
           toolName: block.tool_name,
           input: block.input_preview,
-          state: matchedResult.is_error ? "output-error" : "output-available",
+          state: isToolStillRunning
+            ? "input-available"
+            : matchedResult.is_error
+              ? "output-error"
+              : "output-available",
           output: matchedResult.output_preview,
           errorText: matchedResult.is_error
             ? matchedResult.output_preview || undefined
@@ -736,13 +751,24 @@ export function adaptMessageTurn(
 /**
  * Transform all turns in a conversation to AdaptedMessage[].
  * Internally computes completedToolIds so callers don't need to.
+ *
+ * `inProgressToolCallIdsByIndex` carries the set of tool_call_ids that are
+ * still streaming for each streaming-phase turn (keyed by turn index). The
+ * adapter forwards this to adaptMessageTurn so partial output renders without
+ * flipping the tool out of the running visual state.
  */
 export function adaptMessageTurns(
   turns: MessageTurn[],
   text: AdapterMessageText,
-  streamingIndices?: Set<number>
+  streamingIndices?: Set<number>,
+  inProgressToolCallIdsByIndex?: Map<number, Set<string>>
 ): AdaptedMessage[] {
   return turns.map((turn, i) =>
-    adaptMessageTurn(turn, text, streamingIndices?.has(i) ?? false)
+    adaptMessageTurn(
+      turn,
+      text,
+      streamingIndices?.has(i) ?? false,
+      inProgressToolCallIdsByIndex?.get(i)
+    )
   )
 }