feat: pin sessions to workspace revisions

frontend/src/api/sessions.ts

@@ -1,10 +1,34 @@
 import { apiFetch } from "./client";
+import { getSettings } from "./settings";
+import { workspacePreferences, type WorkspacePreference } from "../workspaces/preferences";
 import type {
   Principal, ResumeSessionResult, SessionScope, SessionSummary, SessionDocument, UiResponse,
 } from "./types";
 
-export const createSession = (i: { question: string; name?: string }) =>
-  apiFetch<{ id: string }>("/sessions", { method: "POST", body: JSON.stringify(i) });
+type NewSessionInput = { question: string; name?: string } & Partial<WorkspacePreference>;
+
+async function selectedPreferences(): Promise<WorkspacePreference> {
+  const saved = workspacePreferences.load();
+  if (saved.workspaceId && saved.provider && saved.model && saved.thinking) return saved;
+
+  // A direct new-session entry point can run before the composer has mounted. Seed its
+  // browser-local preferences from the legacy read-only defaults once, then keep them local.
+  const legacy = await getSettings();
+  return workspacePreferences.save({
+    workspaceId: saved.workspaceId ?? legacy.workspace,
+    provider: saved.provider ?? legacy.provider,
+    model: saved.model ?? legacy.model,
+    thinking: saved.thinking ?? legacy.thinking,
+  });
+}
+
+export async function createSession(i: NewSessionInput) {
+  const preferences = await selectedPreferences();
+  return apiFetch<{ id: string }>("/sessions", {
+    method: "POST",
+    body: JSON.stringify({ ...preferences, ...i }),
+  });
+}
 
 /** Best-effort warm-up; callers must not await it before showing the composer. */
 export const prewarmRuntime = () =>