fix(builder): dedupe page slugs on add/rename/replaceAll (D3)

Two pages that slugify to the same string (e.g. both named "About")
previously both published to about.html, silently overwriting each
other on publish. Add a pure uniqueSlug(base, existingSlugs) helper
that appends -2, -3, ... on collision, and apply it in addPage,
renamePage, and replaceAllPages. The landing page's slug stays locked
to 'index' regardless of collisions, matching existing behavior.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

craft/src/state/PageContext.slug.test.tsx

@@ -0,0 +1,146 @@
+import { describe, test, expect, vi, beforeEach, afterEach } from 'vitest';
+import React from 'react';
+import { createRoot, Root } from 'react-dom/client';
+import { act } from 'react-dom/test-utils';
+import { PageProvider, usePages, uniqueSlug } from './PageContext';
+
+/* PageContext only needs `useEditor` from @craftjs/core (for query.serialize /
+   actions.deserialize during page switches) — mock just that so PageProvider
+   can mount without a real <Editor> tree, following the DOM-harness pattern
+   used in src/ui/AssetPicker.test.tsx (no @testing-library/react in this repo). */
+vi.mock('@craftjs/core', () => ({
+  useEditor: () => ({
+    query: { serialize: () => '{}' },
+    actions: { deserialize: vi.fn() },
+  }),
+}));
+
+/* addPage mints ids from `Date.now()`. Two adds inside the same test can land
+   in the same millisecond and collide on id, which is an existing, unrelated
+   bug (id collision, not slug collision) — out of scope here but it makes
+   these tests flaky since a colliding id defeats the "other pages" slug
+   lookup. Force distinct ids so the slug-dedupe assertions below are stable. */
+let dateNowSpy: ReturnType<typeof vi.spyOn>;
+beforeEach(() => {
+  let counter = 1_700_000_000_000;
+  dateNowSpy = vi.spyOn(Date, 'now').mockImplementation(() => counter++);
+});
+afterEach(() => {
+  dateNowSpy.mockRestore();
+});
+
+let container: HTMLDivElement;
+let root: Root;
+
+function render(ui: React.ReactElement) {
+  container = document.createElement('div');
+  document.body.appendChild(container);
+  act(() => {
+    root = createRoot(container);
+    root.render(ui);
+  });
+}
+
+function unmount() {
+  act(() => {
+    root.unmount();
+  });
+  container.remove();
+}
+
+describe('uniqueSlug', () => {
+  test('returns base unchanged when no collision', () => {
+    expect(uniqueSlug('about', ['index', 'contact'])).toBe('about');
+  });
+
+  test('appends -2 on first collision, -3 on the next, etc', () => {
+    expect(uniqueSlug('about', ['about'])).toBe('about-2');
+    expect(uniqueSlug('about', ['about', 'about-2'])).toBe('about-3');
+  });
+});
+
+describe('PageProvider slug dedupe', () => {
+  test('addPage: two pages with the same name yield distinct slugs', () => {
+    let ctx: ReturnType<typeof usePages> | null = null;
+    const Consumer: React.FC = () => {
+      ctx = usePages();
+      return null;
+    };
+
+    render(
+      <PageProvider>
+        <Consumer />
+      </PageProvider>,
+    );
+
+    act(() => {
+      ctx!.addPage('About', '');
+    });
+    act(() => {
+      ctx!.addPage('About', '');
+    });
+
+    const slugs = ctx!.pages.map((p) => p.slug);
+    expect(slugs).toEqual(['index', 'about', 'about-2']);
+    expect(new Set(slugs).size).toBe(slugs.length);
+
+    unmount();
+  });
+
+  test('renamePage: renaming to an already-used slug is deduped', () => {
+    let ctx: ReturnType<typeof usePages> | null = null;
+    const Consumer: React.FC = () => {
+      ctx = usePages();
+      return null;
+    };
+
+    render(
+      <PageProvider>
+        <Consumer />
+      </PageProvider>,
+    );
+
+    act(() => {
+      ctx!.addPage('About', 'about');
+    });
+    act(() => {
+      ctx!.addPage('Contact', 'contact');
+    });
+
+    const contactPage = ctx!.pages.find((p) => p.name === 'Contact')!;
+    act(() => {
+      ctx!.renamePage(contactPage.id, 'Contact', 'about');
+    });
+
+    const renamed = ctx!.pages.find((p) => p.id === contactPage.id)!;
+    expect(renamed.slug).toBe('about-2');
+
+    const slugs = ctx!.pages.map((p) => p.slug);
+    expect(new Set(slugs).size).toBe(slugs.length);
+
+    unmount();
+  });
+
+  test('landing page slug always stays "index" even if renamed to collide', () => {
+    let ctx: ReturnType<typeof usePages> | null = null;
+    const Consumer: React.FC = () => {
+      ctx = usePages();
+      return null;
+    };
+
+    render(
+      <PageProvider>
+        <Consumer />
+      </PageProvider>,
+    );
+
+    const landingId = ctx!.pages[0].id;
+    act(() => {
+      ctx!.renamePage(landingId, 'Whatever', 'whatever');
+    });
+
+    expect(ctx!.pages[0].slug).toBe('index');
+
+    unmount();
+  });
+});

craft/src/state/PageContext.tsx

@@ -148,6 +148,19 @@ function slugify(name: string): string {
     .replace(/-+/g, '-');
 }
 
+/**
+ * Append `-2`, `-3`, … to `base` until it no longer collides with
+ * `existingSlugs`. Two pages that slugify to the same string (e.g. both
+ * named "About") must not both publish to `about.html` — the second write
+ * would silently overwrite the first on publish.
+ */
+export function uniqueSlug(base: string, existingSlugs: string[]): string {
+  if (!existingSlugs.includes(base)) return base;
+  let i = 2;
+  while (existingSlugs.includes(`${base}-${i}`)) i++;
+  return `${base}-${i}`;
+}
+
 const DEFAULT_PAGE: PageData = {
   id: 'home',
   name: 'Home',
@@ -278,7 +291,7 @@ export const PageProvider: React.FC<{ children: ReactNode }> = ({ children }) =>
 
   const addPage = useCallback(
     (name: string, slug: string) => {
-      const finalSlug = slug || slugify(name);
+      const requestedSlug = slug || slugify(name);
       const id = `page_${Date.now()}`;
 
       // Save current page first
@@ -289,7 +302,7 @@ export const PageProvider: React.FC<{ children: ReactNode }> = ({ children }) =>
         {
           id,
           name,
-          slug: finalSlug,
+          slug: uniqueSlug(requestedSlug, prev.map((p) => p.slug)),
           craftState: null,
           headCode: '',
         },
@@ -335,8 +348,10 @@ export const PageProvider: React.FC<{ children: ReactNode }> = ({ children }) =>
         // First page is the landing page — its slug is locked to 'index' so
         // the file always publishes to index.html regardless of the user-set
         // name. The display name can change freely.
-        const nextSlug = i === 0 ? 'index' : (slug || slugify(name));
+        if (i === 0) return { ...p, name, slug: 'index' };
-        return { ...p, name, slug: nextSlug };
+        const requestedSlug = slug || slugify(name);
+        const otherSlugs = prev.filter((pp) => pp.id !== pageId).map((pp) => pp.slug);
+        return { ...p, name, slug: uniqueSlug(requestedSlug, otherSlugs) };
       }),
     );
   }, []);
@@ -467,16 +482,23 @@ export const PageProvider: React.FC<{ children: ReactNode }> = ({ children }) =>
    */
   const replaceAllPages = useCallback((newPages: { name: string; tree: SerializedTreeNode }[]) => {
     if (newPages.length === 0) return;
-    const built = newPages.map((p, i) => ({
+    // Track slugs as they're assigned so later pages dedupe against earlier
-      id: i === 0 ? 'home' : `page_${Date.now()}_${i}`,
+    // ones in the same batch (e.g. the AI generating two "About" pages).
-      name: p.name,
+    const seenSlugs: string[] = [];
+    const built = newPages.map((p, i) => {
       // First page must publish to index.html so it serves at the site root.
       // Apache resolves '/' to index.html, not home.html — without this, the
       // AI's "Home" page lands at /home.html and visitors hit a blank root.
-      slug: i === 0 ? 'index' : slugify(p.name),
+      const slug = i === 0 ? 'index' : uniqueSlug(slugify(p.name), seenSlugs);
-      craftState: treeToState(p.tree),
+      seenSlugs.push(slug);
-      headCode: '',
+      return {
-    }));
+        id: i === 0 ? 'home' : `page_${Date.now()}_${i}`,
+        name: p.name,
+        slug,
+        craftState: treeToState(p.tree),
+        headCode: '',
+      };
+    });
     setPages(built);
     // Load the first page into the live canvas
     const firstState = built[0].craftState;