feat: UI vue Chat (v0.23.0)

Conversation avec l'agent via POST /api/chat : bulles user/assistant,
état "réfléchit", auto-scroll, gestion d'erreur, déconnexion auto sur 401.
Build OK.

Palier de risque : reversible (front).

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

CHANGELOG.md

@@ -6,6 +6,12 @@ incompatibles. Chaque ligne renvoie à un commit dédié (un artefact = un commi
 
 ## [Unreleased]
 
+## [0.23.0] — 2026-06-23
+### Added
+- UI : vue **Chat** (`web/src/pages/Chat.tsx`) — conversation avec l'agent via
+  `POST /api/chat`, bulles user/assistant, état "réfléchit", auto-scroll, gestion
+  d'erreur, déconnexion auto sur 401. Build OK.
+
 ## [0.22.0] — 2026-06-23
 ### Added
 - Package **`web/`** : scaffold UI (React 19 + Vite 8 + Tailwind 4 + react-router 7,

web/src/pages/Chat.tsx

@@ -1,4 +1,87 @@
-// Vue Chat — remplie en v0.23.0.
-export function Chat() {
-  return <div className="p-6 text-muted">Chat (v0.23.0)…</div>;
+import { useEffect, useRef, useState, type FormEvent } from "react";
+import { useAuth } from "../auth";
+import { api, ApiError } from "../api";
+
+interface Msg {
+  role: "user" | "assistant";
+  text: string;
+}
+
+export function Chat() {
+  const { token, logout } = useAuth();
+  const [messages, setMessages] = useState<Msg[]>([]);
+  const [input, setInput] = useState("");
+  const [busy, setBusy] = useState(false);
+  const [error, setError] = useState<string | null>(null);
+  const bottom = useRef<HTMLDivElement>(null);
+
+  useEffect(() => {
+    bottom.current?.scrollIntoView({ behavior: "smooth" });
+  }, [messages, busy]);
+
+  const send = async (e: FormEvent): Promise<void> => {
+    e.preventDefault();
+    const text = input.trim();
+    if (!text || busy || !token) return;
+    setInput("");
+    setError(null);
+    setMessages((m) => [...m, { role: "user", text }]);
+    setBusy(true);
+    try {
+      const { reply } = await api.chat(token, text);
+      setMessages((m) => [...m, { role: "assistant", text: reply }]);
+    } catch (err) {
+      if (err instanceof ApiError && err.status === 401) {
+        logout();
+        return;
+      }
+      setError(err instanceof Error ? err.message : "Erreur");
+    } finally {
+      setBusy(false);
+    }
+  };
+
+  return (
+    <div className="flex h-full flex-col">
+      <div className="flex-1 overflow-y-auto px-4 py-4 space-y-3">
+        {messages.length === 0 && (
+          <p className="text-muted text-sm">Pose une question à CHLOVA…</p>
+        )}
+        {messages.map((m, i) => (
+          <div key={i} className={m.role === "user" ? "flex justify-end" : "flex justify-start"}>
+            <div
+              className={
+                "max-w-[80%] whitespace-pre-wrap rounded-lg px-3 py-2 text-sm " +
+                (m.role === "user"
+                  ? "bg-surface-2 border border-accent/40"
+                  : "bg-surface border border-border font-mono")
+              }
+            >
+              {m.text}
+            </div>
+          </div>
+        ))}
+        {busy && <p className="text-muted text-sm animate-pulse">CHLOVA réfléchit…</p>}
+        {error && <p role="alert" className="text-danger text-sm">{error}</p>}
+        <div ref={bottom} />
+      </div>
+
+      <form onSubmit={send} className="flex gap-2 border-t border-border bg-surface p-3">
+        <input
+          className="flex-1 rounded-md bg-surface-2 border border-border px-3 py-2 text-fg placeholder:text-muted ring-accent"
+          placeholder="Message…"
+          value={input}
+          onChange={(e) => setInput(e.target.value)}
+          disabled={busy}
+        />
+        <button
+          type="submit"
+          disabled={busy || !input.trim()}
+          className="rounded-md bg-accent px-4 py-2 font-medium text-bg disabled:opacity-50 ring-accent cursor-pointer"
+        >
+          Envoyer
+        </button>
+      </form>
+    </div>
+  );
 }