merge: SP5 live-tail — pub/sub + 3 stream endpoints + frontend tail integration

Brings the SP5 live-tail implementation into main:

Backend
  * EventBus (cyclone.pubsub): per-kind fan-out with drop-oldest overflow
  * FastAPI lifespan initializes the bus + db once per process
  * store.add() publishes claim_written / remittance_written /
    activity_recorded events on every batch write
  * GET /api/{claims,remittances,activity}/stream: NDJSON snapshot +
    live subscription + 15s idle heartbeat
  * EventBus.unsubscribe() lets the tail loop release its queue on
    client disconnect (no queue leak per open stream)

Frontend
  * src/lib/tail-stream.ts: streamTail() async-generator over fetch
  * src/store/tail-store.ts: zustand with FIFO cap 10k per slice
  * src/hooks/useTailStream.ts: connecting/live/reconnecting/stalled/error/closed
    state machine with 1→2→4→8→16→30s backoff
  * src/hooks/useMergedTail.ts: base + tail merge with filter
  * src/components/TailStatusPill.tsx: badge + Reconnect button
  * Claims, Remittances, ActivityLog pages wired to the tail

Tests
  * 437 backend tests pass (was 418 before SP5)
  * 154 frontend tests pass (was 124)
  * npm run typecheck clean
  * end-to-end smoke: open /api/claims/stream, POST 837, see new claims
    arrive in real time without refresh

# Conflicts:
#	src/pages/ActivityLog.tsx
#	src/pages/Remittances.test.tsx
#	src/pages/Remittances.tsx

src/pages/Remittances.tsx

@@ -1,4 +1,4 @@
-import { Fragment, useCallback, useState } from "react";
+import { Fragment, useCallback, useMemo, useState } from "react";
 import { ChevronDown, ChevronRight, Receipt } from "lucide-react";
 import {
   Table,
@@ -17,9 +17,12 @@ import { Pagination } from "@/components/ui/pagination";
 import { KeyboardCheatsheet } from "@/components/KeyboardCheatsheet";
 import { useRemittances } from "@/hooks/useRemittances";
 import { useRowKeyboard } from "@/hooks/useRowKeyboard";
+import { useTailStream } from "@/hooks/useTailStream";
+import { useMergedTail } from "@/hooks/useMergedTail";
+import { TailStatusPill } from "@/components/TailStatusPill";
 import { fmt } from "@/lib/format";
 import { cn } from "@/lib/utils";
-import type { CasAdjustment, RemittanceStatus } from "@/types";
+import type { CasAdjustment, Remittance, RemittanceStatus } from "@/types";
 
 const PAGE_SIZE = 25;
 
@@ -71,7 +74,25 @@ export function Remittances() {
     limit: PAGE_SIZE,
     offset: (page - 1) * PAGE_SIZE,
   });
-  const items = data?.items ?? [];
+
+  // SP5 live-tail wiring (sub-project 5, Phase 5 Task 23). The tail
+  // stream emits every remittance that lands — including ones that
+  // don't match the user's current `status` filter chip. Drop those
+  // tail items so a newly-arrived remit that wouldn't match the page's
+  // intent doesn't flash into the table. Base items are NOT filtered
+  // here (they reflect whatever the list query returned, matching the
+  // existing page behavior).
+  const tailFilterFn = useMemo(
+    () => (r: Remittance) => {
+      if (status && r.status !== status) return false;
+      return true;
+    },
+    [status],
+  );
+
+  const { status: tailStatus, lastEventAt: tailLastEventAt, forceReconnect } =
+    useTailStream("remittances");
+  const items = useMergedTail("remittances", data?.items ?? [], tailFilterFn);
 
   const total = items.reduce(
     (acc, r) => ({
@@ -167,15 +188,25 @@ export function Remittances() {
         </div>
 
         <div className="surface rounded-xl p-4">
-          <FilterChips
-            options={STATUS_OPTIONS}
-            value={status}
-            onChange={(v) => {
-              setStatus((v as RemittanceStatus | null) ?? null);
-              setPage(1);
-            }}
-            eyebrow="Status"
-          />
+          <div className="flex flex-wrap items-center gap-3">
+            <FilterChips
+              options={STATUS_OPTIONS}
+              value={status}
+              onChange={(v) => {
+                setStatus((v as RemittanceStatus | null) ?? null);
+                setPage(1);
+              }}
+              eyebrow="Status"
+            />
+            {/* SP5: live-tail status pill, right-aligned in the toolbar. */}
+            <div className="ml-auto">
+              <TailStatusPill
+                status={tailStatus}
+                lastEventAt={tailLastEventAt}
+                onReconnect={forceReconnect}
+              />
+            </div>
+          </div>
         </div>
 
         <div className="surface rounded-xl overflow-hidden">