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/web/tracker/domain/src/lib/ports/gateways.ts

@@ -19,6 +19,7 @@ import {
   AlertIntegration,
   Comment,
   Decision,
+  Typing,
   Epic,
   GitIntegration,
   GitRepository,
@@ -313,6 +314,15 @@ export abstract class CommentsGateway {
     on: boolean,
   ): Observable<CommandResult>;
   abstract remove(commentId: string): Observable<CommandResult>;
+  /**
+   * Settles a conversation (or reopens it); a conclusion is added as a
+   * reply marked as a decision.
+   */
+  abstract resolveThread(
+    commentId: string,
+    resolved: boolean,
+    conclusion: string | null,
+  ): Observable<CommandResult>;
   /** Marks it as a decision of its ticket (`on`) or unmarks it. */
   abstract markDecision(
     commentId: string,
@@ -496,4 +506,8 @@ export abstract class TrackerRealtimeGateway {
 export abstract class PresenceGateway {
   abstract touch(issueId: string, editing: boolean): Observable<Presence[]>;
   abstract leave(issueId: string): Observable<void>;
+  /** I am writing (an answer to `threadId`, or a new comment). */
+  abstract typing(issueId: string, threadId: string | null): Observable<void>;
+  /** Who is writing on the ticket, as they type (me included). */
+  abstract typists(issueId: string): Observable<Typing>;
 }