feat(notes): compact the operation log and purge old tombstones

- Background job at start and every 6 h: log entries older than 30 days
  (private notes: 7) are removed, documents.log_floor marks the boundary;
  clients behind it get resync and keep their queued changes
- Deleted blocks are purged 30 days after deleted_at via a "purge" log
  effect, so open editors drop them without reloading; a tombstone stays
  while a deleted child still points to it
- Text for a purged block becomes a new block at the end; inserts under a
  purged parent go to the top level (server and browser model)
- doc_op_results kept for 90 days; expired lease/session maps are swept
- Tests: storage, API, engine resync, simulation with compactions

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/lib/docSync/model.ts

@@ -36,7 +36,8 @@ export interface PropsPatch {
   clearConflict?: boolean;
 }
 
-export type OpKind = 'insert' | 'set_content' | 'set_props' | 'move' | 'delete' | 'restore' | 'set_title';
+// 'purge' only appears as a log effect: log compaction removed old tombstones for good
+export type OpKind = 'insert' | 'set_content' | 'set_props' | 'move' | 'delete' | 'restore' | 'set_title' | 'purge';
 
 export interface Op {
   opId: string;
@@ -243,6 +244,9 @@ export function applyEffect(d: Doc, e: Effect): void {
       d.title = e.title || '';
       d.titleVersion = e.titleVersion || 0;
       break;
+    case 'purge':
+      for (const id of e.ids || []) d.blocks.delete(id);
+      break;
   }
 }
 
@@ -295,8 +299,8 @@ export function applyOp(d: Doc, op: Op, by = '', conflictId: (opId: string) => s
       if (d.blocks.has(op.blockId)) return reject('exists');
       let parent = op.parentId || '';
       if (parent) {
-        if (!d.blocks.has(parent)) return reject('parent_missing');
-        parent = liveAncestor(d, parent);
+        // A purged parent (compaction) puts the block at the top level, like the server
+        parent = d.blocks.has(parent) ? liveAncestor(d, parent) : '';
       }
       if (!op.orderKey || !validOrderKey(op.orderKey)) return reject('invalid_order_key');
       emit({
@@ -313,8 +317,15 @@ export function applyOp(d: Doc, op: Op, by = '', conflictId: (opId: string) => s
     }
     case 'set_content': {
       const b = d.blocks.get(op.blockId || '');
-      if (!b) return reject('missing');
       if (op.content === undefined) return reject('no_content');
+      if (!b) {
+        // The block was purged (offline for weeks): like the server, the text becomes a new block at the end
+        if (!op.content || !op.blockId || op.blockId.length > 64) return reject('missing');
+        const roots = children(d, '');
+        const key = keyBetween(roots.length ? roots[roots.length - 1].orderKey : '', '');
+        emit({ kind: 'insert', blockId: op.blockId, parentId: '', orderKey: key, type: 'bullet', content: op.content, props: {}, version: 1 });
+        return done({ status: 'applied', version: 1, reason: 'revived' });
+      }
       if (b.deleted) restore([b.id]);
       if (op.content === b.content) return done({ status: 'applied', version: b.version });
       if ((op.baseVersion ?? 0) !== b.version) {