fix: prevent run completion race condition with consecutive stability checks

pollForCompletion exited immediately when session went idle before agent
created TODOs or registered children (0 todos + 0 children = vacuously
complete). Add consecutive stability checks (3x500ms debounce) and
currentTool guard to prevent premature exit.

Extract pollForCompletion to dedicated module for testability.

src/cli/run/runner.ts

@@ -1,6 +1,5 @@
 import pc from "picocolors"
 import type { RunOptions, RunContext } from "./types"
-import { checkCompletionConditions } from "./completion"
 import { createEventState, processEvents, serializeError } from "./events"
 import { loadPluginConfig } from "../../plugin-config"
 import { createServerConnection } from "./server-connection"
@@ -8,10 +7,10 @@ import { resolveSession } from "./session-resolver"
 import { createJsonOutputManager } from "./json-output"
 import { executeOnCompleteHook } from "./on-complete-hook"
 import { resolveRunAgent } from "./agent-resolver"
+import { pollForCompletion } from "./poll-for-completion"
 
 export { resolveRunAgent }
 
-const POLL_INTERVAL_MS = 500
 const DEFAULT_TIMEOUT_MS = 0
 
 export async function run(options: RunOptions): Promise<number> {
@@ -124,30 +123,4 @@ export async function run(options: RunOptions): Promise<number> {
   }
 }
 
-async function pollForCompletion(
-  ctx: RunContext,
-  eventState: ReturnType<typeof createEventState>,
-  abortController: AbortController
-): Promise<number> {
-  while (!abortController.signal.aborted) {
-    await new Promise((resolve) => setTimeout(resolve, POLL_INTERVAL_MS))
 
-    if (!eventState.mainSessionIdle) continue
-
-    if (eventState.mainSessionError) {
-      console.error(pc.red(`\n\nSession ended with error: ${eventState.lastError}`))
-      console.error(pc.yellow("Check if todos were completed before the error."))
-      return 1
-    }
-
-    if (!eventState.hasReceivedMeaningfulWork) continue
-
-    const shouldExit = await checkCompletionConditions(ctx)
-    if (shouldExit) {
-      console.log(pc.green("\n\nAll tasks completed."))
-      return 0
-    }
-  }
-
-  return 130
-}