timers: drop retired surface timer ids

yasl_surface_del_timer zeroed its entry and kept it. A one-shot surface
timer that fired stayed in the surface's id list until the surface was
destroyed. A client that re-arms a one-shot timer, such as a cursor
blink, grew the list without bound, and each delete scanned all of it.

Delete now removes the entry. Before the list grows, add drops the ids
that the loop has retired. The list holds only armed timers.

Delete now returns false for a timer that already retired, as
yasl_loop_del_timer does.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/common/loop.h b/src/common/loop.h
index 579fa2c..663417a 100644
--- a/src/common/loop.h
+++ b/src/common/loop.h
@@ -4,5 +4,7 @@
 #include "yasl/loop.h"
 
 int yasl_loop_next_timeout_ms(const struct yasl_loop *l);
+/* Whether id is armed: added, not deleted, and not retired by its callback. */
+bool yasl_loop_timer_armed(const struct yasl_loop *l, yasl_timer_id id);
 
 #endif /* YASL_COMMON_LOOP_H */