loops-wizard: initial_burst + on_artifact_update trigger UI

Surfaces the two new trigger fields shipped in the previous commit so
users can compose the new loop patterns without editing raw jsonb.

Step 4 (Triggers) now has five toggles instead of three:
1. **Run at create-time (initial burst)** — number input, defaults to 1
   so every new loop runs at least once. Toggle off = classic behavior
   (no auto-fire).
2. Cron schedule (existing)
3. On previous completion (existing) — pairs with initial_burst > 1
   for a back-to-back burst chain, and with cron for continuous
   iteration between schedule ticks.
4. **On new research artifact** — visible always; auto-disabled with
   an explanatory label when no source topic is bound. Coalesced
   server-side against in-flight runs so rapid revisions don't spawn
   duplicates.
5. Webhook (existing)

Body wiring:
- Sends initial_burst > 0 → { initial_burst: N } in triggers jsonb.
- Sends on_artifact_update only when a source topic is bound (safety
  belt matching the backend's fan-out filter).

Step gate:
- Advancing from step 4 now requires ANY one of the five triggers
  (was just the three legacy toggles). The initial_burst default of 1
  means users can happy-path through this step without deliberate
  action, which is the intended nudge — every loop should have at
  least one path to run.

Read/write parity:
- readInitialTriggers grows two fields so edit-mode reflects existing
  loops' triggers correctly.

Next commit lands ResearchWizard's "When should this run?" step +
optional paired coding loop, and after that the kind='research'
dispatch path.

frontend/src/components/dashboard/LoopsWizard.tsx

@@ -103,6 +103,18 @@ export function LoopsWizard({
   const [webhookEnabled, setWebhookEnabled] = useState(
     !!initialTriggers.webhook_enabled,
   );
+  // NEW — initial_burst: how many iterations to fire back-to-back on
+  // create. Default 1 so every loop runs at least once (D1).
+  const [initialBurst, setInitialBurst] = useState<number>(
+    typeof initialTriggers.initial_burst === "number"
+      ? initialTriggers.initial_burst
+      : 1,
+  );
+  // NEW — on_artifact_update: wake up when the source topic gets a new
+  // outcome. Only meaningful when a source_research_topic is bound.
+  const [onArtifactUpdate, setOnArtifactUpdate] = useState<boolean>(
+    !!initialTriggers.on_artifact_update,
+  );
   const [repeatKind, setRepeatKind] = useState<"infinite" | "iters" | "until">(
     initialRepeat.kind,
   );
@@ -211,7 +223,12 @@ export function LoopsWizard({
     (step === 1 && title.trim().length > 0) ||
     step === 2 ||
     (step === 3 && task.trim().length > 0 && graphReady) ||
-    (step === 4 && (cronEnabled || onCompletion || webhookEnabled)) ||
+    (step === 4 &&
+      (cronEnabled ||
+        onCompletion ||
+        webhookEnabled ||
+        initialBurst > 0 ||
+        (onArtifactUpdate && !!sourceTopicId))) ||
     step === 5 ||
     step === 6;
 
@@ -262,6 +279,10 @@ export function LoopsWizard({
           ...(cronEnabled ? { cron: cron.trim() } : {}),
           ...(onCompletion ? { on_completion: true } : {}),
           ...(webhookEnabled ? { webhook_enabled: true } : {}),
+          ...(initialBurst > 0 ? { initial_burst: initialBurst } : {}),
+          ...(onArtifactUpdate && sourceTopicId
+            ? { on_artifact_update: true }
+            : {}),
         },
         repeat_policy,
         ...(repo ? { repo } : {}),
@@ -481,6 +502,28 @@ export function LoopsWizard({
           {!noAgents && step === 4 && (
             <div style={{ display: "flex", flexDirection: "column", gap: 12 }}>
               <span style={labelStyle}>Triggers (pick any combination)</span>
+              <TriggerToggle
+                on={initialBurst > 0}
+                onToggle={(on) => setInitialBurst(on ? Math.max(1, initialBurst) : 0)}
+                label="Run at create-time (initial burst)"
+                hint="Fire N iterations back-to-back when the loop is created. Default 1 = runs at least once."
+              >
+                {initialBurst > 0 && (
+                  <div style={{ display: "flex", alignItems: "center", gap: 8 }}>
+                    <input
+                      type="number"
+                      min={1}
+                      max={100}
+                      value={initialBurst}
+                      onChange={(e) => setInitialBurst(Math.max(1, Number(e.target.value) || 1))}
+                      style={{ ...fieldStyle, width: 90, fontFamily: mono }}
+                    />
+                    <span style={{ fontFamily: mono, fontSize: 11, color: "#8a8a92" }}>
+                      iteration{initialBurst === 1 ? "" : "s"} back-to-back
+                    </span>
+                  </div>
+                )}
+              </TriggerToggle>
               <TriggerToggle
                 on={cronEnabled}
                 onToggle={setCronEnabled}
@@ -502,6 +545,16 @@ export function LoopsWizard({
                 label="On previous completion"
                 hint="Enqueue the next iteration as soon as the previous one emits run_completed."
               />
+              <TriggerToggle
+                on={onArtifactUpdate && !!sourceTopicId}
+                onToggle={(on) => setOnArtifactUpdate(on)}
+                label={
+                  sourceTopicId
+                    ? "On new research artifact"
+                    : "On new research artifact (bind a source topic first)"
+                }
+                hint="Wake up whenever the bound research topic writes a fresh outcome version. Coalesced with any in-flight run."
+              />
               <TriggerToggle
                 on={webhookEnabled}
                 onToggle={setWebhookEnabled}
@@ -1041,6 +1094,8 @@ function readInitialTriggers(t: unknown): {
   cron?: string;
   on_completion?: boolean;
   webhook_enabled?: boolean;
+  initial_burst?: number;
+  on_artifact_update?: boolean;
 } {
   if (!t || typeof t !== "object") return {};
   const o = t as Record<string, unknown>;
@@ -1048,6 +1103,9 @@ function readInitialTriggers(t: unknown): {
     cron: typeof o.cron === "string" ? o.cron : undefined,
     on_completion: !!o.on_completion,
     webhook_enabled: !!o.webhook_enabled,
+    initial_burst:
+      typeof o.initial_burst === "number" ? o.initial_burst : undefined,
+    on_artifact_update: !!o.on_artifact_update,
   };
 }