fix(ci): require a default export before treating a file as a route entry (#7028)

* fix(ci): require a default export before treating a file as a route entry

Follow-up to #7026, which added `error.tsx` to the entry filenames and with it
picked up `[workspaceId]/components/error/error.tsx` — named like a boundary,
and not one. It exports `ErrorShell` and `ErrorState` for the thirteen real
boundaries to use; Next would reject it as a boundary for having no default
export. Counting it inflated the coverage number and would have recorded a
shared component in the graph-weight baseline as though it were a route.

The filename was never the right test. Every convention-composed entry must
default-export the thing Next renders, so that is the discriminator now. Entry
count goes 60 → 59, and all thirteen real `error.tsx` boundaries still walk.

Also adds `template.tsx` and `default.tsx`. Neither exists under
`app/workspace` today, so this changes nothing now — but the enumeration claims
to cover what Next composes, and leaving two out makes that claim false the day
someone adds one.

Both raised in review on #7026 (Cursor and Greptile respectively); I merged
before reading them, so this lands separately.

* fix(ci): count every form that declares a default export

`export { default } from './page'` is a valid Next entry and the regex required
`as default`, so such an entry would have dropped out of the walk and skipped
both the registry gate and the graph-weight ratchet — silently, which is the
dangerous direction for a discriminator to fail in.

Latent rather than live: the form appears once under `app/workspace`, in a
barrel, not in an entry filename.

Four forms now count — `export default …`, `export { default } from`,
`export { default, … } from`, and `export { X as default }`.
`export { default as X }` still does not: it re-exports another module's default
under a name and leaves this one without one. Verified all ten variants,
including that last distinction.

Raised by both Cursor and Greptile on #7028.

scripts/check-tool-registry-boundary.ts

@@ -72,13 +72,46 @@ const ENTRY_FILENAMES = new Set([
   'error.tsx',
   'loading.tsx',
   'not-found.tsx',
+  'template.tsx',
+  'default.tsx',
 ])
 
+/**
+ * A default export, which every convention-composed entry must have — Next
+ * renders the default and nothing else.
+ *
+ * The filename alone is not enough. `[workspaceId]/components/error/error.tsx`
+ * is named like a boundary and is not one: it exports `ErrorShell` and
+ * `ErrorState` for the thirteen real boundaries to use, and Next would reject
+ * it as a boundary for having no default. Counting it as an entry both inflated
+ * the coverage number and would have recorded a shared component in the
+ * graph-weight baseline as though it were a route.
+ *
+ * All four declaring forms count — `export default …`, `export { default } from`,
+ * `export { default, … } from`, and `export { X as default }`. `export { default
+ * as X }` does not: it re-exports someone else's default under a name and leaves
+ * the module without one. Missing a form is the dangerous direction, since the
+ * entry would drop out of the walk and skip both the registry gate and the
+ * graph-weight ratchet silently.
+ */
+const DEFAULT_EXPORT_RE =
+  /(?:^|\n)\s*export\s+default\b|(?:^|\n)\s*export\s*\{[^}]*(?:\bas\s+default\b|\bdefault\s*[,}])/
+
+function hasDefaultExport(file: string): boolean {
+  try {
+    return DEFAULT_EXPORT_RE.test(readFileSync(file, 'utf8'))
+  } catch {
+    return false
+  }
+}
+
 function collectEntries(dir: string, found: string[] = []): string[] {
   for (const entry of readdirSync(dir, { withFileTypes: true })) {
     const full = join(dir, entry.name)
     if (entry.isDirectory()) collectEntries(full, found)
-    else if (ENTRY_FILENAMES.has(entry.name)) found.push(relative(APP, full))
+    else if (ENTRY_FILENAMES.has(entry.name) && hasDefaultExport(full)) {
+      found.push(relative(APP, full))
+    }
   }
   return found
 }