M8: posting a comment in the browser no longer stops the app (#1764)

The event log read the clock through std::time::SystemTime and Instant, which panic on wasm32-unknown-unknown ("time not implemented on this platform"). Every mutating comment.* command appends an event, so the first comment posted in the web build hit it. The log now takes SystemTime, UNIX_EPOCH and Instant from web_time, as the rest of the engine does. A test checks the stamp is a current Unix time read through the same clock.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

crates/engine/src/events.rs

@@ -7,10 +7,14 @@
 
 use std::collections::VecDeque;
 use std::sync::{Condvar, Mutex, PoisonError};
-use std::time::{Duration, Instant, SystemTime, UNIX_EPOCH};
+use std::time::Duration;
 
 use serde::Serialize;
 use serde_json::Value;
+// The browser build has no `std` clock: `std::time::SystemTime::now()` panics on
+// wasm32-unknown-unknown ("time not implemented on this platform"), and every `comment.*` command
+// stamps an event. `web_time` is `std::time` on native targets and the JavaScript clock on wasm.
+use web_time::{Instant, SystemTime, UNIX_EPOCH};
 
 /// Most events kept; the oldest are dropped.
 pub const MAX_EVENTS: usize = 1024;

crates/engine/src/events_tests.rs

@@ -44,6 +44,18 @@ fn events_keep_sequence_and_filter_topics() {
     assert_eq!(r.events[0].kind, "document.changed");
 }
 
+#[test]
+fn events_are_stamped_with_the_wall_clock() {
+    // The stamp is read through `web_time`, the clock the browser build has as well: with
+    // `std::time::SystemTime` every comment posted on the web panicked (#1764).
+    let log = EventLog::default();
+    log.push("comment.added", "Doc", None, json!({"commentId": 1}));
+    let r = log.poll(0, &comments(), 10, Duration::ZERO);
+    let now = web_time::SystemTime::now().duration_since(web_time::UNIX_EPOCH).unwrap().as_secs_f64();
+    let time = r.events[0].time;
+    assert!(time > 1_700_000_000.0 && time <= now, "{time} is seconds since the Unix epoch, read just before {now}");
+}
+
 #[test]
 fn a_poll_wakes_for_a_push() {
     let log = Arc::new(EventLog::default());