feat(tickets): surface frontend V1 du système de tickets

Surface UI complète des tickets (domaine Issue exposé « ticket »),
validée QA de bout en bout : cargo build + tests backend verts,
npm run build + npm test (459) verts.

- Domaine : DTO Ticket, 9 events Issue* + guard isTicketEvent.
- Ports : TicketGateway (+ types query/input) ajouté à Gateways.
- Adapters : TauriTicketGateway réel (+ isTicketVersionConflict),
  wiring, et MockTicketGateway pour les tests.
- Feature tickets : hooks (useTickets, useTicketDetail,
  useProjectAgents), TicketsPanel, TicketDetail, TicketsView,
  ticketMeta + tests.
- ProjectsView : onglet sidebar « Tickets ».

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/features/tickets/useTickets.ts

@@ -0,0 +1,96 @@
+/**
+ * View-model hook for the project ticket list (F2).
+ *
+ * Consumes the {@link TicketGateway} for reads/creates and subscribes to the
+ * `Issue*` domain events (via {@link SystemGateway}) to refresh the list on any
+ * ticket mutation — including those made by agents through MCP. Filters/search
+ * are part of the query and drive a re-fetch when they change.
+ */
+
+import { useCallback, useEffect, useMemo, useState } from "react";
+
+import { isTicketEvent, type GatewayError, type Ticket, type TicketList } from "@/domain";
+import type { CreateTicketInput, TicketListQuery } from "@/ports";
+import { useGateways } from "@/app/di";
+
+export interface TicketsViewModel {
+  list: TicketList | null;
+  error: string | null;
+  busy: boolean;
+  query: TicketListQuery;
+  setQuery: (next: TicketListQuery) => void;
+  refresh: () => Promise<void>;
+  create: (input: CreateTicketInput) => Promise<Ticket | null>;
+}
+
+function describe(e: unknown): string {
+  if (e && typeof e === "object" && "message" in e) {
+    return String((e as GatewayError).message);
+  }
+  return String(e);
+}
+
+export function useTickets(projectId: string): TicketsViewModel {
+  const { ticket, system } = useGateways();
+  const [list, setList] = useState<TicketList | null>(null);
+  const [error, setError] = useState<string | null>(null);
+  const [busy, setBusy] = useState(false);
+  const [query, setQuery] = useState<TicketListQuery>({});
+
+  // Stable dependency key so `refresh` only changes when a filter actually does.
+  const queryKey = useMemo(() => JSON.stringify(query), [query]);
+
+  const refresh = useCallback(async () => {
+    setBusy(true);
+    setError(null);
+    try {
+      setList(await ticket.list(projectId, query));
+    } catch (e) {
+      setError(describe(e));
+    } finally {
+      setBusy(false);
+    }
+    // `query` is captured via `queryKey`; listing it directly would rebuild the
+    // callback on every render (a new object identity each time).
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [projectId, ticket, queryKey]);
+
+  const create = useCallback(
+    async (input: CreateTicketInput): Promise<Ticket | null> => {
+      setError(null);
+      try {
+        const created = await ticket.create(projectId, input);
+        await refresh();
+        return created;
+      } catch (e) {
+        setError(describe(e));
+        return null;
+      }
+    },
+    [projectId, ticket, refresh],
+  );
+
+  useEffect(() => {
+    void refresh();
+  }, [refresh]);
+
+  useEffect(() => {
+    if (!system) return;
+    let unsubscribe: (() => void) | undefined;
+    let cancelled = false;
+    void system
+      .onDomainEvent((event) => {
+        if (isTicketEvent(event)) void refresh();
+      })
+      .then((u) => {
+        if (cancelled) u();
+        else unsubscribe = u;
+      });
+    return () => {
+      cancelled = true;
+      unsubscribe?.();
+    };
+  }, [refresh, system]);
+
+  return { list, error, busy, query, setQuery, refresh, create };
+}