feat(ui): profils locaux/LAN OpenAI-compatible dans le first-run et les terminaux (#14)

Câble la surface frontend des profils IA locaux/LAN OpenAI-compatible,
en parité avec l'adapter backend additif (aab4bca).

- domain: types de profil OpenAI-compatible
- first-run: édition/validation du profil dans le FirstRunWizard
- adapters/mock: mock de profil pour les tests
- terminals: rendu des round-trips et erreurs endpoint (role=alert)

Validé QA (frontend GO): typecheck exit 0, vitest 59 fichiers / 566 tests,
0 echec ; couverture timeouts round-trip + erreur endpoint role=alert
prouvees ; pas de regression sur les tests de bail headless.

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

frontend/src/features/terminals/TerminalView.tsx

@@ -32,7 +32,7 @@
  *   fresh one. If the session is gone (was explicitly closed), it opens fresh.
  */
 
-import { useEffect, useRef } from "react";
+import { useEffect, useRef, useState } from "react";
 
 import { Terminal } from "@xterm/xterm";
 import { FitAddon } from "@xterm/addon-fit";
@@ -108,6 +108,12 @@ export function TerminalView({
 }: TerminalViewProps) {
   const { terminal } = useGateways();
   const containerRef = useRef<HTMLDivElement | null>(null);
+  // A user-visible launch failure (e.g. an OpenAI-compatible endpoint that is
+  // unreachable). Rendered as a DOM `role="alert"` banner over the cell so the
+  // failure is always visible and accessible — not only painted into the xterm
+  // buffer (which is invisible to assistive tech and absent when xterm can't
+  // mount). `null` ⇒ no error. The cell stays mounted and IdeA stays usable.
+  const [openError, setOpenError] = useState<string | null>(null);
 
   // The opener (`open` or the terminal gateway) is read through a ref so the
   // effect does NOT depend on its identity. Otherwise every parent re-render
@@ -138,6 +144,9 @@ export function TerminalView({
     const reattacher = reattachRef.current ?? tgw?.reattach.bind(tgw);
     if (!container || !opener) return;
 
+    // Fresh (re)mount: clear any prior failure banner before we try to open.
+    setOpenError(null);
+
     const term = new Terminal({
       convertEol: false,
       cursorBlink: true,
@@ -218,6 +227,10 @@ export function TerminalView({
         );
         return;
       }
+      // A genuine launch failure (unreachable endpoint, model missing, network
+      // drop…). Surface it as an accessible DOM banner AND as a red line in the
+      // buffer. The cell renders as failed; IdeA stays usable (other cells work).
+      setOpenError(`Échec du lancement de l'agent : ${describe(e)}`);
       term.write(
         `\r\n\x1b[31mfailed to open terminal: ${describe(e)}\x1b[0m\r\n`,
       );
@@ -307,10 +320,41 @@ export function TerminalView({
 
   return (
     <div
-      ref={containerRef}
       data-testid="terminal-view"
-      style={{ width: "100%", height: "100%", minHeight: "16rem" }}
-    />
+      style={{
+        position: "relative",
+        width: "100%",
+        height: "100%",
+        minHeight: "16rem",
+      }}
+    >
+      {/* xterm mounts into this inner node; the error banner is a sibling so
+          React never fights xterm over the same subtree. */}
+      <div ref={containerRef} style={{ width: "100%", height: "100%" }} />
+      {openError && (
+        <div
+          role="alert"
+          data-testid="terminal-error"
+          style={{
+            position: "absolute",
+            top: 0,
+            left: 0,
+            right: 0,
+            padding: "0.5rem 0.75rem",
+            background: "rgba(120, 20, 20, 0.92)",
+            color: "#fff",
+            fontSize: 13,
+            fontFamily:
+              'ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace',
+            whiteSpace: "pre-wrap",
+            wordBreak: "break-word",
+            zIndex: 3,
+          }}
+        >
+          {openError}
+        </div>
+      )}
+    </div>
   );
 }