Fix review findings: autosave leak and permalink bypassing resume

- composition.ts: put() now removes the superseded save blob once the new
  record and index are safely written, instead of leaving every prior
  autosave orphaned in localStorage under its old saveId.
- PlayApp.tsx: the ?campaign= auto-start effect now checks findLocalSave()
  first and resumes an existing run, matching the manual briefing path
  instead of always starting a fresh session.
- PlayApp.test.tsx: covers the permalink-resume path.

Author: The-Running-Dev

site/src/play/PlayApp.test.tsx

@@ -111,6 +111,43 @@ describe("PlayApp cabinet presentation", () => {
     }
   });
 
+  it("resumes an existing local save when opened via its permanent ?campaign= link, rather than restarting", async () => {
+    const user = userEvent.setup();
+    const { unmount } = render(<PlayApp />);
+    await screen.findByRole("heading", { name: "Adventure disk library" });
+
+    await user.click(screen.getByRole("button", { name: /The Bureaucracy/i }));
+    await user.click(
+      screen.getByRole("button", { name: "Load selected adventure" }),
+    );
+    await user.click(
+      await screen.findByRole("button", {
+        name: /Wait for the municipal registry/i,
+      }),
+    );
+    const advancedScene =
+      document.querySelector(".scene-body")?.textContent ?? "";
+    expect(advancedScene).not.toMatch(/handwritten/i);
+    unmount();
+
+    const originalLocation = window.location.href;
+    window.history.pushState({}, "", "/?campaign=bulgaria-bureaucracy");
+    try {
+      render(<PlayApp />);
+      expect(
+        await screen.findByRole("heading", { name: "The Bureaucracy" }),
+      ).toBeVisible();
+      expect(document.querySelector(".scene-body")?.textContent).toBe(
+        advancedScene,
+      );
+      expect(
+        screen.queryByRole("heading", { name: "Adventure disk library" }),
+      ).not.toBeInTheDocument();
+    } finally {
+      window.history.pushState({}, "", originalLocation);
+    }
+  });
+
   it("ignores a submission that resolves after the player quits to the library", async () => {
     const user = userEvent.setup();
     render(<PlayApp />);

site/src/play/PlayApp.tsx

@@ -169,7 +169,9 @@ function PlayAppReady({ demo }: { demo: BrowserDemo }) {
     if (!requested || !demo.findCampaign(requested)) return;
     autoStarted.current = true;
     setSelectedId(requested);
-    void start(requested);
+    const saveId = demo.findLocalSave(requested);
+    if (saveId) void resume(requested, saveId);
+    else void start(requested);
   }, [demo]);
 
   function reducedMotion(): boolean {

site/src/play/composition.ts

@@ -55,11 +55,20 @@ function localPersistence(): SessionPersistence {
         return raw ? (JSON.parse(raw) as StoredSaveRecord) : undefined;
       },
       async put(record) {
+        const supersededId = localStorage.getItem(
+          campaignSaveIndexKey(record.campaignId),
+        );
         localStorage.setItem(saveKey(record.saveId), JSON.stringify(record));
         localStorage.setItem(
           campaignSaveIndexKey(record.campaignId),
           record.saveId,
         );
+        // Every autosave mints a fresh saveId (types.ts), so the previous full
+        // record would otherwise sit in localStorage unreachable from the index.
+        // Removed only after the new record and index are safely written, so a
+        // failure here can never erase the only usable checkpoint.
+        if (supersededId && supersededId !== record.saveId)
+          localStorage.removeItem(saveKey(supersededId));
       },
       async delete(id) {
         const raw = await this.get(id);