fix(todo-continuation-enforcer): add stagnation limit constant

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

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

src/hooks/todo-continuation-enforcer/constants.ts

@@ -18,5 +18,6 @@ export const COUNTDOWN_GRACE_PERIOD_MS = 500
 
 export const ABORT_WINDOW_MS = 3000
 export const CONTINUATION_COOLDOWN_MS = 5_000
+export const MAX_STAGNATION_COUNT = 3
 export const MAX_CONSECUTIVE_FAILURES = 5
 export const FAILURE_RESET_WINDOW_MS = 5 * 60 * 1000