fix(todo-continuation-enforcer): track continuation stagnation state

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

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

@@ -0,0 +1,49 @@
+import { afterEach, beforeEach, describe, expect, test } from "bun:test"
+
+import { createSessionStateStore, type SessionStateStore } from "./session-state"
+
+describe("createSessionStateStore", () => {
+  let sessionStateStore: SessionStateStore
+
+  beforeEach(() => {
+    sessionStateStore = createSessionStateStore()
+  })
+
+  afterEach(() => {
+    sessionStateStore.shutdown()
+  })
+
+  test("given repeated incomplete counts after a continuation, tracks stagnation", () => {
+    // given
+    const sessionID = "ses-stagnation"
+    const state = sessionStateStore.getState(sessionID)
+    state.lastInjectedAt = Date.now()
+
+    // when
+    const firstUpdate = sessionStateStore.trackContinuationProgress(sessionID, 2)
+    const secondUpdate = sessionStateStore.trackContinuationProgress(sessionID, 2)
+    const thirdUpdate = sessionStateStore.trackContinuationProgress(sessionID, 2)
+
+    // then
+    expect(firstUpdate.stagnationCount).toBe(0)
+    expect(secondUpdate.stagnationCount).toBe(1)
+    expect(thirdUpdate.stagnationCount).toBe(2)
+  })
+
+  test("given incomplete count decreases, resets stagnation tracking", () => {
+    // given
+    const sessionID = "ses-progress-reset"
+    const state = sessionStateStore.getState(sessionID)
+    state.lastInjectedAt = Date.now()
+    sessionStateStore.trackContinuationProgress(sessionID, 3)
+    sessionStateStore.trackContinuationProgress(sessionID, 3)
+
+    // when
+    const progressUpdate = sessionStateStore.trackContinuationProgress(sessionID, 2)
+
+    // then
+    expect(progressUpdate.hasProgressed).toBe(true)
+    expect(progressUpdate.stagnationCount).toBe(0)
+    expect(sessionStateStore.getState(sessionID).lastIncompleteCount).toBe(2)
+  })
+})

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

@@ -10,9 +10,17 @@ interface TrackedSessionState {
   lastAccessedAt: number
 }
 
+export interface ContinuationProgressUpdate {
+  previousIncompleteCount?: number
+  stagnationCount: number
+  hasProgressed: boolean
+}
+
 export interface SessionStateStore {
   getState: (sessionID: string) => SessionState
   getExistingState: (sessionID: string) => SessionState | undefined
+  trackContinuationProgress: (sessionID: string, incompleteCount: number) => ContinuationProgressUpdate
+  resetContinuationProgress: (sessionID: string) => void
   cancelCountdown: (sessionID: string) => void
   cleanup: (sessionID: string) => void
   cancelAllCountdowns: () => void
@@ -46,6 +54,7 @@ export function createSessionStateStore(): SessionStateStore {
     }
 
     const state: SessionState = {
+      stagnationCount: 0,
       consecutiveFailures: 0,
     }
     sessions.set(sessionID, { state, lastAccessedAt: Date.now() })
@@ -61,6 +70,57 @@ export function createSessionStateStore(): SessionStateStore {
     return undefined
   }
 
+  function trackContinuationProgress(
+    sessionID: string,
+    incompleteCount: number
+  ): ContinuationProgressUpdate {
+    const state = getState(sessionID)
+    const previousIncompleteCount = state.lastIncompleteCount
+
+    state.lastIncompleteCount = incompleteCount
+
+    if (previousIncompleteCount === undefined) {
+      state.stagnationCount = 0
+      return {
+        previousIncompleteCount,
+        stagnationCount: state.stagnationCount,
+        hasProgressed: false,
+      }
+    }
+
+    if (incompleteCount < previousIncompleteCount) {
+      state.stagnationCount = 0
+      return {
+        previousIncompleteCount,
+        stagnationCount: state.stagnationCount,
+        hasProgressed: true,
+      }
+    }
+
+    if (state.lastInjectedAt === undefined) {
+      return {
+        previousIncompleteCount,
+        stagnationCount: state.stagnationCount,
+        hasProgressed: false,
+      }
+    }
+
+    state.stagnationCount += 1
+    return {
+      previousIncompleteCount,
+      stagnationCount: state.stagnationCount,
+      hasProgressed: false,
+    }
+  }
+
+  function resetContinuationProgress(sessionID: string): void {
+    const state = getExistingState(sessionID)
+    if (!state) return
+
+    state.lastIncompleteCount = undefined
+    state.stagnationCount = 0
+  }
+
   function cancelCountdown(sessionID: string): void {
     const tracked = sessions.get(sessionID)
     if (!tracked) return
@@ -100,6 +160,8 @@ export function createSessionStateStore(): SessionStateStore {
   return {
     getState,
     getExistingState,
+    trackContinuationProgress,
+    resetContinuationProgress,
     cancelCountdown,
     cleanup,
     cancelAllCountdowns,