feat(notes): show block locks and presence, conflict copies with accept/discard, undo/redo

Phase 3 of the collaboration plan:
- Blocks held by someone else show a lock with the name and are read-only;
  Enter in such a block adds a new block below. Delete, merge, indent and
  drag are not started when a involved block (or one in its branch) is
  locked; a short notice explains why (fixes FLAW-25).
- Presence: the editor header lists who else has the note open.
- Conflict copies are highlighted ("Konflikt – Version von …") with
  Übernehmen (replaces the original or the title) and Verwerfen. Both check
  the locks of the original and of the copy first.
- Undo/redo of own changes (Ctrl/Cmd+Z, Ctrl+Shift+Z, Ctrl+Y, beforeinput
  history events): typing is grouped per block until a 1 s pause, up to 200
  steps per tab; a step is skipped with a notice if someone else changed or
  holds the block meanwhile. New clearConflict props patch on the server.
- New blocks get focus synchronously on mount (fixes FLAW-26).
- Fix: after reopening a note from local storage the engine polled every
  30 s instead of 3 s until the next change, because the delay was decided
  before the first response told it the note is shared.
- Tests: undo/conflict engine tests, lock/undo/conflict UI tests and
  e2e/lock.e2e.mjs (two browsers); all three browser tests pass against a
  freshly built image.

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

frontend/src/lib/docSync/__tests__/undo.test.ts

@@ -0,0 +1,184 @@
+import { describe, it, expect } from 'vitest';
+import type { DocumentBlock } from '../../types';
+import { DocSyncEngine } from '../engine';
+import { applyOp, Doc, emptyDoc, Op, Result } from '../model';
+import { MemoryStorage } from '../persist';
+import { LogEntry, SyncRequest, Transport, TransportError } from '../transport';
+
+/** Minimal stand-in server (same rules as the Go server, plus configurable leases of others). */
+class Server {
+  doc: Doc = emptyDoc();
+  log: LogEntry[] = [];
+  results = new Map<string, Result>();
+  othersLeases: { blockId: string; userId: string; name: string }[] = [];
+
+  constructor(blocks: [string, string][]) {
+    blocks.forEach(([id, content], i) => this.apply({ opId: `seed${i}`, kind: 'insert', blockId: id, parentId: '', orderKey: `a${i}`, content }, 'seed'));
+  }
+  apply(op: Op, by: string): Result {
+    const known = this.results.get(op.opId);
+    if (known) return known;
+    const { effects, result } = applyOp(this.doc, op, by);
+    for (const e of effects) this.log.push({ seq: this.log.length + 1, userId: by, clientId: by, opId: op.opId, effect: e });
+    if (effects.length) result.seq = this.log.length;
+    this.results.set(op.opId, result);
+    return result;
+  }
+  transport(): Transport {
+    return {
+      snapshot: async () => ({
+        docId: 'd',
+        title: this.doc.title,
+        titleVersion: this.doc.titleVersion,
+        headSeq: this.log.length,
+        blocks: Array.from(this.doc.blocks.values()).map((b) => ({ ...b, props: { ...b.props } })),
+        role: 'owner',
+        shared: true,
+      }),
+      sync: async (_id: string, body: SyncRequest) => {
+        if (!body) throw new TransportError('x', 0);
+        const results = body.ops.map((op) => this.apply(op, body.clientId));
+        return {
+          results,
+          ops: this.log.filter((e) => e.seq > body.lastSeq),
+          headSeq: this.log.length,
+          hasMore: false,
+          role: 'owner',
+          shared: true,
+          sessions: 2,
+          presence: [],
+          leases: { granted: [], denied: [], others: this.othersLeases },
+        };
+      },
+      leave: async () => {},
+    };
+  }
+}
+
+let clock = 1_000_000;
+async function engineFor(server: Server) {
+  const e = new DocSyncEngine('d', { transport: server.transport(), storage: new MemoryStorage(), manual: true, now: () => clock });
+  await e.start();
+  return e;
+}
+const flat = (e: DocSyncEngine) => e.getState().blocks;
+const texts = (e: DocSyncEngine) => flat(e).map((b) => b.content);
+function edit(e: DocSyncEngine, fn: (b: DocumentBlock[]) => DocumentBlock[]) {
+  e.applyFlat(fn(flat(e).map((b) => ({ ...b }))));
+}
+
+describe('undo/redo', () => {
+  it('groups typing in one block and reverts it in one step', async () => {
+    const server = new Server([['a', 'Hallo']]);
+    const e = await engineFor(server);
+    edit(e, (b) => [{ ...b[0], content: 'Hallo W' }]);
+    clock += 300;
+    edit(e, (b) => [{ ...b[0], content: 'Hallo Welt' }]);
+    expect(e.undo().ok).toBe(true);
+    expect(texts(e)).toEqual(['Hallo']);
+    expect(e.getState().canUndo).toBe(false);
+    expect(e.redo().ok).toBe(true);
+    expect(texts(e)).toEqual(['Hallo Welt']);
+    await e.syncNow();
+    expect(server.doc.blocks.get('a')!.content).toBe('Hallo Welt');
+  });
+
+  it('separates typing steps after a pause', async () => {
+    const server = new Server([['a', '']]);
+    const e = await engineFor(server);
+    edit(e, (b) => [{ ...b[0], content: 'Eins' }]);
+    clock += 2000;
+    edit(e, (b) => [{ ...b[0], content: 'Eins Zwei' }]);
+    e.undo();
+    expect(texts(e)).toEqual(['Eins']);
+  });
+
+  it('undoes inserting and deleting blocks', async () => {
+    const server = new Server([['a', 'Erster']]);
+    const e = await engineFor(server);
+    edit(e, (b) => [...b, { id: 'n', type: 'bullet', content: 'Neu', level: 0 }]);
+    clock += 2000;
+    edit(e, (b) => b.filter((x) => x.id !== 'a'));
+    expect(texts(e)).toEqual(['Neu']);
+    e.undo();
+    expect(texts(e)).toEqual(['Erster', 'Neu']);
+    e.undo();
+    expect(texts(e)).toEqual(['Erster']);
+    await e.syncNow();
+    expect(server.doc.blocks.get('a')!.deleted).toBe(false);
+    expect(server.doc.blocks.get('n')!.deleted).toBe(true);
+  });
+
+  it('skips undo when someone else changed the block in between', async () => {
+    const server = new Server([['a', 'Start']]);
+    const e = await engineFor(server);
+    edit(e, (b) => [{ ...b[0], content: 'Meins' }]);
+    await e.syncNow();
+    server.apply({ opId: 'other', kind: 'set_content', blockId: 'a', baseVersion: 2, content: 'Fremd' }, 'other');
+    await e.syncNow();
+    const res = e.undo();
+    expect(res.ok).toBe(false);
+    expect(res.message).toMatch(/jemand anderem/);
+    expect(texts(e)).toEqual(['Fremd']);
+  });
+
+  it('skips undo on a block someone else is editing', async () => {
+    const server = new Server([['a', 'Start']]);
+    const e = await engineFor(server);
+    edit(e, (b) => [{ ...b[0], content: 'Meins' }]);
+    await e.syncNow();
+    server.othersLeases = [{ blockId: 'a', userId: 'u2', name: 'Anna' }];
+    await e.syncNow();
+    const res = e.undo();
+    expect(res.ok).toBe(false);
+    expect(res.message).toMatch(/Anna/);
+    expect(texts(e)).toEqual(['Meins']);
+  });
+});
+
+describe('conflict copies', () => {
+  async function withConflict() {
+    const server = new Server([['a', 'Start']]);
+    const e = await engineFor(server);
+    server.apply({ opId: 'first', kind: 'set_content', blockId: 'a', baseVersion: 1, content: 'Gewinner' }, 'other');
+    server.apply({ opId: 'second', kind: 'set_content', blockId: 'a', baseVersion: 1, content: 'Verlierer' }, 'mine');
+    await e.syncNow();
+    const copy = flat(e).find((b) => b.conflictOf === 'a')!;
+    return { server, e, copy };
+  }
+
+  it('accepting replaces the original text and removes the copy', async () => {
+    const { server, e, copy } = await withConflict();
+    expect(e.resolveConflict(copy.id, true).ok).toBe(true);
+    expect(texts(e)).toEqual(['Verlierer']);
+    await e.syncNow();
+    expect(server.doc.blocks.get('a')!.content).toBe('Verlierer');
+    expect(server.doc.blocks.get(copy.id)!.deleted).toBe(true);
+    e.undo();
+    expect(texts(e)).toEqual(['Gewinner', 'Verlierer']);
+  });
+
+  it('is not started while someone else holds the copy', async () => {
+    const { server, e, copy } = await withConflict();
+    server.othersLeases = [{ blockId: copy.id, userId: 'u2', name: 'Ben' }];
+    await e.syncNow();
+    const res = e.resolveConflict(copy.id, true);
+    expect(res.ok).toBe(false);
+    expect(res.message).toMatch(/Ben/);
+    expect(texts(e)).toEqual(['Gewinner', 'Verlierer']);
+  });
+
+  it('discarding removes only the copy', async () => {
+    const { e, copy } = await withConflict();
+    e.resolveConflict(copy.id, false);
+    expect(texts(e)).toEqual(['Gewinner']);
+  });
+
+  it('a copy whose original is gone becomes a normal block', async () => {
+    const { server, e, copy } = await withConflict();
+    server.apply({ opId: 'del', kind: 'delete', blockId: 'a' }, 'other');
+    await e.syncNow();
+    e.resolveConflict(copy.id, true);
+    expect(flat(e).find((b) => b.id === copy.id)?.conflictOf).toBeUndefined();
+  });
+});