feat: pin sessions to workspace revisions

frontend/src/workspaces/preferences.test.ts

@@ -0,0 +1,15 @@
+import { expect, test } from "vitest";
+import { workspacePreferences } from "./preferences";
+
+test("migrates legacy selections once and keeps later browser choices", () => {
+  localStorage.clear();
+
+  expect(workspacePreferences.migrate({
+    workspaceId: "psd-clinical", provider: "zai", model: "glm-5.2", thinking: "medium",
+  })).toMatchObject({ workspaceId: "psd-clinical", model: "glm-5.2" });
+  workspacePreferences.save({ workspaceId: "research", provider: "deepseek", model: "deepseek-v4-pro", thinking: "high" });
+
+  expect(workspacePreferences.migrate({ workspaceId: "legacy" })).toMatchObject({
+    workspaceId: "research", provider: "deepseek", model: "deepseek-v4-pro", thinking: "high",
+  });
+});

frontend/src/workspaces/preferences.ts

@@ -0,0 +1,40 @@
+export interface WorkspacePreference {
+  workspaceId?: string;
+  provider?: string;
+  model?: string;
+  thinking?: string;
+}
+
+const STORAGE_KEY = "thothii.workspace-registry.v1.preferences";
+
+function storage(): Storage | undefined {
+  try { return window.localStorage; } catch { return undefined; }
+}
+
+function parse(raw: string | null): WorkspacePreference | undefined {
+  if (raw === null) return undefined;
+  try {
+    const value = JSON.parse(raw);
+    return value && typeof value === "object" && !Array.isArray(value) ? value as WorkspacePreference : undefined;
+  } catch {
+    return undefined;
+  }
+}
+
+/** Anonymous, non-secret browser choices for the workspace session composer. */
+export const workspacePreferences = {
+  load(): WorkspacePreference {
+    return parse(storage()?.getItem(STORAGE_KEY) ?? null) ?? {};
+  },
+
+  save(value: WorkspacePreference): WorkspacePreference {
+    try { storage()?.setItem(STORAGE_KEY, JSON.stringify(value)); } catch { /* storage is optional */ }
+    return value;
+  },
+
+  /** Copy the pre-local-storage server values only when this browser has no saved choice. */
+  migrate(legacy: WorkspacePreference): WorkspacePreference {
+    const current = storage()?.getItem(STORAGE_KEY);
+    return current === null || current === undefined ? this.save(legacy) : this.load();
+  },
+};