feat: conversations on a ticket are settled, and you see who is typing

A top-level comment and its replies can be resolved by whoever can
change the ticket (CommentThreadResolvedEvent), with an optional
conclusion added as a reply marked as a decision, so it shows above the
ticket. A settled conversation folds to one line (topic, who settled it
and the conclusion) and can be unfolded or reopened; the header counts
the open ones, and finishing the ticket with one open asks first.

«Ana está escribiendo…» shows in the conversation being answered, at
once: a `typing` mutation publishes to a Redis channel per ticket
(`typing` subscription), never stored. In replies, Enter sends and
Shift+Enter breaks the line, except inside lists and code.

API: resolveThread / PUT-DELETE /api/comments/{id}/resolution, Comment
.resolved/resolvedBy/resolvedAt, typing mutation and subscription. MCP:
resolve_thread.

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

libs/api/tracker/application/src/lib/event-handlers/comment-thread-resolved.event-handler.ts

@@ -0,0 +1,28 @@
+import { EventsHandler, IEventHandler } from '@nestjs/cqrs';
+import { CommentThreadResolvedEvent } from '@task-stream/api/tracker/domain';
+import { UpsertMaterializedCommentRepository } from '../ports/upsert-materialized-comment.repository';
+import { UserDirectory } from '../ports/user-directory';
+import { ReadModelNotifier, versionOf } from './read-model-notifier';
+
+@EventsHandler(CommentThreadResolvedEvent)
+export class CommentThreadResolvedEventHandler
+  implements IEventHandler<CommentThreadResolvedEvent>
+{
+  constructor(
+    private readonly upsertMaterializedCommentRepository: UpsertMaterializedCommentRepository,
+    private readonly users: UserDirectory,
+    private readonly notifier: ReadModelNotifier,
+  ) {}
+
+  async handle(event: CommentThreadResolvedEvent) {
+    const refs = await this.users.refs([event.actorId]);
+    await this.upsertMaterializedCommentRepository.upsert({
+      id: event.aggregateId,
+      resolved: event.resolved,
+      resolvedBy: event.resolved ? refs.of(event.actorId) : null,
+      resolvedAt: event.resolved ? event.occurredAt : null,
+      version: versionOf(event),
+    });
+    await this.notifier.comment(event.aggregateId, event.issueId, event);
+  }
+}