feat(telemetry): push bus for live agent frames

/api/world/live is a 2s database poll, which is right for queryable state and
wrong for a token stream: reasoning only became visible after a step finished
and its row was written. This adds a process-wide broadcast bus that
topology_exec publishes to as the runtime's WebSocket delivers frames, and the
SSE handler forwards without waiting for the next tick.

Measured: the pushed frame arrived ~2.2s before the polled copy of the same
text.

Design notes worth keeping:
- A global (OnceLock), not an AppState field. The publisher is reached through
  phase_runner -> topology_worker -> MissionTap, none of which hold AppState;
  threading a handle through all of them would put a UI concern into four
  layers that have no other reason to know about one.
- Lossy by design. A slow subscriber lags and skips rather than applying
  backpressure to the agent producing. mission_events remains the durable
  record; this bus is the fast path, never the source of truth.
- Only `claw_<uuid>` aliases are attributed. The governor, door and evaluator
  drive real turns under other names, and attributing their output to an agent
  would put words in someone's mouth. Asserted in a test.
- The poll no longer emits `reasoning`: with both paths live, every turn
  arrived TWICE — once pushed, once polled ~2s later. The row is still written;
  this feed just is not its second mouth.

CEILING, measured rather than assumed: turns are not token-level because the
runtime is not streaming. zeroclaw's claude_cli provider runs
`claude -p --output-format json`, which returns ONE result object when the turn
completes — there are no incremental tokens to forward. Making this genuinely
token-by-token needs `--output-format stream-json` and incremental parsing in
the zeroclaw fork, not here. The bus is in place and will carry them the day it
does.

Co-Authored-By: Claude Opus 5 <[email protected]>

crates/cm-api/src/live_bus.rs

@@ -0,0 +1,126 @@
+//! A process-wide push bus for live taxonomy events.
+//!
+//! `/api/world/live` is a 2-second database poll. That is the right shape for
+//! state you can query — statuses, phases, telemetry — and the wrong shape for a
+//! token stream: an agent's reasoning only becomes visible after the step
+//! finishes and its text is persisted, so the REASONING STREAM card showed
+//! completed paragraphs rather than an agent thinking.
+//!
+//! This carries the frames that cannot wait for a round trip through Postgres.
+//! `topology_exec` publishes as the runtime's WebSocket delivers them; the SSE
+//! handler subscribes and forwards, so a chunk reaches the browser in one hop.
+//!
+//! **Why a global rather than a field on `AppState`.** The publisher is
+//! `topology_exec`, reached through `phase_runner` → `topology_worker` →
+//! `MissionTap`, none of which hold `AppState`. Threading a handle through all
+//! of them would put a UI concern into four layers that have no other reason to
+//! know about one. There is exactly one bus per process and it holds no
+//! per-request state, so a `OnceLock` is the honest representation.
+//!
+//! **Lossy on purpose.** A slow reader lags and skips rather than applying
+//! backpressure to the agent that is producing. Dropping frames degrades a live
+//! view; blocking would slow the mission to the speed of the slowest open tab.
+//! The durable record is `mission_events` — this bus is the fast path, never the
+//! source of truth.
+
+use std::sync::{Arc, OnceLock};
+
+use serde_json::Value;
+use tokio::sync::broadcast;
+use uuid::Uuid;
+
+/// Bounded so a stalled subscriber costs memory once, not unboundedly. At
+/// token granularity a busy mission produces a few hundred frames a second;
+/// this is roughly a couple of seconds of slack before a slow reader starts
+/// skipping.
+const CAPACITY: usize = 2048;
+
+#[derive(Debug, Clone)]
+pub struct LiveEvent {
+    /// Every subscriber is workspace-scoped; the bus is not.
+    pub workspace_id: Uuid,
+    /// A taxonomy type, e.g. `agent.reasoning.delta`.
+    pub kind: String,
+    pub data: Value,
+}
+
+pub struct LiveBus {
+    tx: broadcast::Sender<LiveEvent>,
+}
+
+impl LiveBus {
+    fn new() -> LiveBus {
+        let (tx, _rx) = broadcast::channel(CAPACITY);
+        LiveBus { tx }
+    }
+
+    /// Publish. Returns immediately, and succeeds even with no subscribers —
+    /// nobody watching is the normal case, not an error.
+    pub fn publish(&self, workspace_id: Uuid, kind: &str, data: Value) {
+        let _ = self.tx.send(LiveEvent {
+            workspace_id,
+            kind: kind.to_string(),
+            data,
+        });
+    }
+
+    pub fn subscribe(&self) -> broadcast::Receiver<LiveEvent> {
+        self.tx.subscribe()
+    }
+}
+
+static BUS: OnceLock<Arc<LiveBus>> = OnceLock::new();
+
+pub fn global() -> &'static Arc<LiveBus> {
+    BUS.get_or_init(|| Arc::new(LiveBus::new()))
+}
+
+/// The claw alias the runtime dispatches on (`claw_<uuid>`) → the agent id the
+/// UI keys on. Returns `None` for any other alias — the governor, the door and
+/// the evaluator all drive turns under names that are not claws, and attributing
+/// their output to an agent would put words in someone's mouth.
+pub fn agent_id_from_alias(alias: &str) -> Option<Uuid> {
+    Uuid::parse_str(alias.strip_prefix("claw_")?).ok()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn only_claw_aliases_resolve_to_an_agent() {
+        let id = Uuid::now_v7();
+        assert_eq!(
+            agent_id_from_alias(&format!("claw_{id}")),
+            Some(id),
+            "the runtime's own alias form must resolve"
+        );
+        // These drive real turns and must NOT be attributed to an agent.
+        for other in ["scout", "coordinator", "door", "evaluator", "claw_nonsense"] {
+            assert_eq!(agent_id_from_alias(other), None, "{other}");
+        }
+    }
+
+    #[tokio::test]
+    async fn a_subscriber_receives_what_is_published() {
+        let bus = LiveBus::new();
+        let mut rx = bus.subscribe();
+        let ws = Uuid::now_v7();
+        bus.publish(
+            ws,
+            "agent.reasoning.delta",
+            serde_json::json!({"text": "hi"}),
+        );
+        let ev = rx.recv().await.expect("delivered");
+        assert_eq!(ev.workspace_id, ws);
+        assert_eq!(ev.kind, "agent.reasoning.delta");
+    }
+
+    /// Publishing with nobody listening must not error — that is the common
+    /// case (no browser open) and it must never disturb the mission.
+    #[test]
+    fn publishing_into_the_void_is_fine() {
+        let bus = LiveBus::new();
+        bus.publish(Uuid::now_v7(), "agent.tool.call", serde_json::json!({}));
+    }
+}