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/comments.service.ts

@@ -11,6 +11,7 @@ import { DeleteCommentCommand } from './commands/delete-comment.command';
 import { EditCommentCommand } from './commands/edit-comment.command';
 import { ReactToCommentCommand } from './commands/react-to-comment.command';
 import { MarkDecisionCommand } from './commands/mark-decision.command';
+import { ResolveThreadCommand } from './commands/resolve-thread.command';
 import { Page } from './ports/find-issues.repository';
 import { GetCommentsQuery } from './queries/get-comments.query';
 import {
@@ -69,6 +70,21 @@ export class CommentsService {
     );
   }
 
+  /**
+   * Settles a conversation or reopens it; a conclusion stays as a reply
+   * marked as a decision.
+   */
+  resolveThread(
+    actorId: string,
+    commentId: string,
+    resolved: boolean,
+    conclusion: string | null = null,
+  ): Promise<CommandResult> {
+    return this.commands.execute(
+      new ResolveThreadCommand(actorId, commentId, resolved, conclusion),
+    );
+  }
+
   /** A ticket's decisions, oldest first. */
   decisions(
     viewerId: string | null,