fix(todo-continuation): remove activity-based stagnation bypass

Activity signals (tool calls like compress, grep, bash) were treated as
'progress' by the stagnation detector, resetting the stagnation counter
every cycle. This prevented MAX_STAGNATION_COUNT from being reached,
causing infinite continuation loops when models degrade to minimal
responses in long sessions (e.g. GLM-5.1 at ~100K tokens).

Stagnation now only tracks actual todo state changes: incomplete count
decrease, completed count increase, or todo snapshot change. Tool-level
activity no longer resets the stagnation counter.

src/hooks/todo-continuation-enforcer/session-state.ts

@@ -1,4 +1,4 @@
-import type { ContinuationProgressOptions, SessionState, Todo } from "./types"
+import type { SessionState, Todo } from "./types"
 
 type TimerHandle = number | { unref?: () => void }
 
@@ -16,8 +16,6 @@ interface TrackedSessionState {
   lastAccessedAt: number
   lastCompletedCount?: number
   lastTodoSnapshot?: string
-  activitySignalCount: number
-  lastObservedActivitySignalCount?: number
 }
 
 export interface ContinuationProgressUpdate {
@@ -25,19 +23,17 @@ export interface ContinuationProgressUpdate {
   previousStagnationCount: number
   stagnationCount: number
   hasProgressed: boolean
-  progressSource: "none" | "todo" | "activity"
+  progressSource: "none" | "todo"
 }
 
 export interface SessionStateStore {
   getState: (sessionID: string) => SessionState
   getExistingState: (sessionID: string) => SessionState | undefined
   startPruneInterval: () => void
-  recordActivity: (sessionID: string) => void
   trackContinuationProgress: (
     sessionID: string,
     incompleteCount: number,
     todos?: Todo[],
-    options?: ContinuationProgressOptions,
   ) => ContinuationProgressUpdate
   resetContinuationProgress: (sessionID: string) => void
   cancelCountdown: (sessionID: string) => void
@@ -113,7 +109,6 @@ export function createSessionStateStore(): SessionStateStore {
     const trackedSession: TrackedSessionState = {
       state: rawState,
       lastAccessedAt: Date.now(),
-      activitySignalCount: 0,
     }
     sessions.set(sessionID, trackedSession)
     return trackedSession
@@ -132,16 +127,10 @@ export function createSessionStateStore(): SessionStateStore {
     return undefined
   }
 
-  function recordActivity(sessionID: string): void {
-    const trackedSession = getTrackedSession(sessionID)
-    trackedSession.activitySignalCount += 1
-  }
-
   function trackContinuationProgress(
     sessionID: string,
     incompleteCount: number,
     todos?: Todo[],
-    options: ContinuationProgressOptions = {},
   ): ContinuationProgressUpdate {
     const trackedSession = getTrackedSession(sessionID)
     const state = trackedSession.state
@@ -149,7 +138,6 @@ export function createSessionStateStore(): SessionStateStore {
     const previousStagnationCount = state.stagnationCount
     const currentCompletedCount = todos?.filter((todo) => todo.status === "completed").length
     const currentTodoSnapshot = todos ? getTodoSnapshot(todos) : undefined
-    const currentActivitySignalCount = trackedSession.activitySignalCount
     const hasCompletedMoreTodos =
       currentCompletedCount !== undefined
       && trackedSession.lastCompletedCount !== undefined
@@ -158,10 +146,6 @@ export function createSessionStateStore(): SessionStateStore {
       currentTodoSnapshot !== undefined
       && trackedSession.lastTodoSnapshot !== undefined
       && currentTodoSnapshot !== trackedSession.lastTodoSnapshot
-    const hasObservedExternalActivity =
-      options.allowActivityProgress === true
-      && trackedSession.lastObservedActivitySignalCount !== undefined
-      && currentActivitySignalCount > trackedSession.lastObservedActivitySignalCount
     const hadSuccessfulInjectionAwaitingProgressCheck = state.awaitingPostInjectionProgressCheck === true
 
     state.lastIncompleteCount = incompleteCount
@@ -171,7 +155,6 @@ export function createSessionStateStore(): SessionStateStore {
     if (currentTodoSnapshot !== undefined) {
       trackedSession.lastTodoSnapshot = currentTodoSnapshot
     }
-    trackedSession.lastObservedActivitySignalCount = currentActivitySignalCount
 
     if (previousIncompleteCount === undefined) {
       state.stagnationCount = 0
@@ -184,13 +167,9 @@ export function createSessionStateStore(): SessionStateStore {
       }
     }
 
-    const progressSource = incompleteCount < previousIncompleteCount || hasCompletedMoreTodos || hasTodoSnapshotChanged
-      ? "todo"
-      : hasObservedExternalActivity
-        ? "activity"
-        : "none"
+    const hasProgressed = incompleteCount < previousIncompleteCount || hasCompletedMoreTodos || hasTodoSnapshotChanged
 
-    if (progressSource !== "none") {
+    if (hasProgressed) {
       state.stagnationCount = 0
       state.awaitingPostInjectionProgressCheck = false
       return {
@@ -198,7 +177,7 @@ export function createSessionStateStore(): SessionStateStore {
         previousStagnationCount,
         stagnationCount: state.stagnationCount,
         hasProgressed: true,
-        progressSource,
+        progressSource: "todo",
       }
     }
 
@@ -236,8 +215,6 @@ export function createSessionStateStore(): SessionStateStore {
     state.awaitingPostInjectionProgressCheck = false
     trackedSession.lastCompletedCount = undefined
     trackedSession.lastTodoSnapshot = undefined
-    trackedSession.activitySignalCount = 0
-    trackedSession.lastObservedActivitySignalCount = undefined
   }
 
   function cancelCountdown(sessionID: string): void {
@@ -282,7 +259,6 @@ export function createSessionStateStore(): SessionStateStore {
     getState,
     getExistingState,
     startPruneInterval,
-    recordActivity,
     trackContinuationProgress,
     resetContinuationProgress,
     cancelCountdown,