fix(retry): prevent retry flush from consuming shutdown timeout

Drop the delayed retry_poll_task before bgworker_flush to prevent it
from delaying the flush_task by min(retry_interval, timeout). Subtract
elapsed flush time from the shutdown timeout so the total is bounded.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: jpnurmi

src/sentry_retry.c

@@ -314,10 +314,22 @@ retry_flush_task(void *_retry, void *_state)
     }
 }
 
+static bool
+drop_task_cb(void *_data, void *_ctx)
+{
+    (void)_data;
+    (void)_ctx;
+    return true;
+}
+
 void
 sentry__retry_flush(sentry_retry_t *retry, uint64_t timeout)
 {
     if (retry) {
+        // drop the delayed poll that would stall bgworker_flush
+        sentry__bgworker_foreach_matching(
+            retry->bgworker, retry_poll_task, drop_task_cb, NULL);
+        sentry__atomic_store(&retry->scheduled, 0);
         sentry__bgworker_submit(retry->bgworker, retry_flush_task, NULL, retry);
         sentry__bgworker_flush(retry->bgworker, timeout);
     }

src/transports/sentry_http_transport.c

@@ -305,10 +305,12 @@ http_transport_shutdown(uint64_t timeout, void *transport_state)
     sentry_bgworker_t *bgworker = transport_state;
     http_transport_state_t *state = sentry__bgworker_get_state(bgworker);
 
-    // flush drains in-flight retries; shutdown is near-instant afterward
+    uint64_t started = sentry__monotonic_time();
     sentry__retry_flush(state->retry, timeout);
+    uint64_t elapsed = sentry__monotonic_time() - started;
+    uint64_t remaining = elapsed < timeout ? timeout - elapsed : 0;
 
-    int rv = sentry__bgworker_shutdown(bgworker, timeout);
+    int rv = sentry__bgworker_shutdown(bgworker, remaining);
     if (rv != 0) {
         sentry__retry_dump_queue(state->retry, http_send_task);
         if (state->shutdown_client) {