feat: replies to comments

A comment can answer another one (replyTo), one level deep: answering a
reply joins the same thread, and it must be on the same ticket. Whoever
wrote the comment gets a new REPLIED notification, and the activity says
"respondió a un comentario".

A comment deleted while it has replies stays, without its text
(deleted: true), so the thread still reads; it goes with its last reply
and does not count in commentCount.

The ticket page shows threads with their replies indented and a
"Responder" box; REST, GraphQL and the MCP (add_comment, get_issue) take
and show replyTo. Existing comments are unchanged. Docs, Word and PDF
updated.

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

apps/mcp/src/app/tools/issues.resolver.ts

@@ -224,9 +224,10 @@ export class IssuesResolver {
             )
           ).items.map((c) => ({
             id: c.id,
-            author: c.author.name,
+            replyTo: c.replyTo,
+            author: c.deleted ? null : c.author.name,
             at: c.createdAt,
-            body: c.body,
+            body: c.deleted ? '(deleted; kept for its replies)' : c.body,
           }))
         : undefined;
       const history = params.withHistory
@@ -411,19 +412,27 @@ export class IssuesResolver {
 
   @Tool({
     name: 'add_comment',
-    description: 'Comment on a ticket (decisions, explanations, steps).',
+    description:
+      'Comment on a ticket (decisions, explanations, steps), or answer a comment with replyTo (one level: answering a reply joins its thread).',
     paramsSchema: z.object({
       issue: issueRef,
       body: z.string().min(1).max(20000),
+      replyTo: z
+        .string()
+        .optional()
+        .describe('Id of the comment it answers (see get_issue)'),
     }),
     annotations: WRITE,
   })
-  comment({ issue, body }: { issue: string; body: string }, ctx: McpContext) {
+  comment(
+    { issue, body, replyTo }: { issue: string; body: string; replyTo?: string },
+    ctx: McpContext,
+  ) {
     return toolResult(() =>
       this.api.data(
         this.api.as(ctx).POST('/api/issues/{issue}/comments', {
           params: { path: { issue } },
-          body: { body },
+          body: { body, replyTo },
         }),
       ),
     );