Date sitemap lastmod from the build pipeline; warn on skipped pages

- bunext build records when each page's client bundle hash last changed
  in .bunext/page-lastmod.json (sitemap.lastmod_file to relocate). The
  hash covers the page's whole import graph, so component edits re-date
  every page that uses them. The sitemap uses these dates as lastmod
- Add sitemap.default_lastmod
- BREAKING: use_file_lastmod now defaults to false (file mtimes are reset
  by checkouts); it is a fallback after the build record
- Warn when a page or __root.tsx is skipped because its default export
  is not at the start of a line (e.g. export { Page as default })
- Replace leaking module mocks in tests (log, grab-root-file-path) with
  spies and fixtures

Co-Authored-By: Claude Opus 5.5 <[email protected]>

dist/utils/generate-sitemap.js

@@ -7,6 +7,7 @@ import grabOrigin from "./grab-origin";
 import grabRelativePath from "./grab-relative-path";
 import isDevelopment from "./is-development";
 import { log } from "./log";
+import { readPageLastmodRecord } from "./page-lastmod-record";
 const ErrorPagePaths = ["/404", "/500"];
 /**
  * Protocol limits for a single sitemap file
@@ -131,7 +132,8 @@ function parseLastmod(lastmod) {
     return isNaN(date.getTime()) ? undefined : date;
 }
 export async function grabSitemapEntries(params) {
-    const use_file_lastmod = params?.use_file_lastmod ?? true;
+    const use_file_lastmod = params?.use_file_lastmod ?? false;
+    const lastmod_record = readPageLastmodRecord(params?.lastmod_file);
     const entries = [];
     const pages = grabAllPages({ exclude_api: true });
     for (let i = 0; i < pages.length; i++) {
@@ -145,17 +147,26 @@ export async function grabSitemapEntries(params) {
             file_path: page.local_path,
             route: page_path,
         });
+        // When the page's client bundle last changed, per `bunext build`
+        const build_lastmod = lastmod_record?.pages[grabRelativePath(page.local_path)]?.lastmod;
         if (page_sitemap_paths) {
-            entries.push(...page_sitemap_paths.map(toSitemapEntry));
+            for (const page_sitemap_path of page_sitemap_paths) {
+                const entry = toSitemapEntry(page_sitemap_path);
+                entries.push({
+                    ...entry,
+                    lastmod: entry.lastmod || build_lastmod,
+                });
+            }
             continue;
         }
         if (page.url_path.match(/\[/))
             continue;
         entries.push({
             path: page_path,
-            lastmod: use_file_lastmod
-                ? statSync(page.local_path).mtime
-                : undefined,
+            lastmod: build_lastmod ||
+                (use_file_lastmod
+                    ? statSync(page.local_path).mtime
+                    : undefined),
         });
     }
     const additional_paths = typeof params?.additional_paths == "function"
@@ -172,10 +183,11 @@ export async function grabSitemapEntries(params) {
             continue;
         seen.add(path);
         final_entries.push({
-            changefreq: params?.default_changefreq,
-            priority: params?.default_priority,
             ...entry,
             path,
+            lastmod: entry.lastmod || params?.default_lastmod,
+            changefreq: entry.changefreq || params?.default_changefreq,
+            priority: entry.priority ?? params?.default_priority,
         });
     }
     return final_entries;