fix: unique addPage ids + collision-free scopeId hashing

M-3: PageContext.addPage minted ids from bare `page_${Date.now()}` --
two adds inside the same millisecond collided on id, so a subsequent
rename/delete/save silently acted on both pages at once. Added a
module-scoped monotonic counter combined with the timestamp
(nextPageId(), exported for direct unit testing) and used it
everywhere an addPage-style id is minted (addPage, replaceAllPages).

M-4: scopeId() lowercased + stripped non-alphanumeric characters from
the node id into a slug, so two node ids differing only by
case/punctuation (e.g. "AbC" vs "abc", or "a-b" vs "ab") collapsed
onto the same scope -- defeating the whole point of scoping ids per
node (M-1/Menu/Tabs/ColumnLayout/Gallery/etc. all rely on it). Now
hashes the raw node id via the existing djb2 stableHash() instead of
slugifying it: still deterministic (same id -> same scope) and a valid
CSS ident, but collision-resistant across case/punctuation. This
changes the exact scope strings Menu/Tabs/ColumnLayout/Gallery/etc.
emit -- expected and fine, since none of their tests pinned an exact
scope value (all already asserted structure/uniqueness).

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

craft/src/utils/escape.ts

@@ -151,8 +151,14 @@ export function stableHash(seed: string): string {
  * available.
  */
 export function scopeId(nodeId: string | undefined, fallbackSeed: string, prefix: string): string {
-  const slug = (nodeId || '').toString().toLowerCase().replace(/[^a-z0-9]+/g, '');
-  return `${prefix}_${slug || stableHash(fallbackSeed)}`;
+  // M-4: hash the raw node id (via the same djb2 `stableHash` used for the
+  // fallback path below) rather than lowercasing + stripping punctuation
+  // into a slug. A slug collapses distinct ids that differ only by
+  // case/punctuation (e.g. "AbC" and "abc", or "a-b" and "ab") onto the same
+  // scope; hashing the untouched string keeps them distinct while staying
+  // deterministic and producing a valid CSS ident (prefix + '_' + [a-z0-9]+).
+  const seed = (nodeId || '').toString();
+  return `${prefix}_${stableHash(seed || fallbackSeed)}`;
 }
 
 // Shared enum allowlists for `toHtml` attribute sinks fed by props that are