fix: prevent TUI freeze on massive bash output and fix spinner rendering (#500)

- Sync OutputSink.push(): eliminate promise chain per chunk, buffer
  management and onChunk run inline, file writes deferred via queue
- 64KB native read buffer (was 4KB): reduces chunk count ~16x
- chunkThrottleMs in OutputSink: gate onChunk to every 50ms
- BashExecutionComponent streaming throttle: gate + 100-line cap
- Remove requestRender from chunk callbacks: spinner drives renders
- Remove double sanitization in appendOutput (already done by OutputSink)
- Inline SEGMENT_RESET in TUI doRender buffer writes: eliminates O(N)
  string allocations per frame from #applyLineResets
- Cache header Text in BashExecutionComponent (created once, reused)
- Gate sixel mask computation behind protocol + passthrough check
- Fix spinner: #spinnerFrame made optional, interval calls #updateDisplay
- Remove pendingChunks promise chains from bash-executor and bash-interactive

packages/coding-agent/src/tools/python.ts

@@ -289,8 +289,8 @@ export class PythonTool implements AgentTool<typeof pythonSchema> {
 				const executorOptions: PythonExecutorOptions = {
 					...baseExecutorOptions,
 					reset: isFirstCell ? reset : false,
-					onChunk: async chunk => {
-						await outputSink!.push(chunk);
+					onChunk: chunk => {
+						outputSink!.push(chunk);
 					},
 				};