feat: presence on tickets

A ticket's page beats every 10 s (touchPresence / PUT
/issues/{issue}/presence, with whether I am editing) and gets back who
else is there, editing ones first. Entries live in Redis, one hash per
ticket, and fade after 30 s without a beat; leaving the page takes me out
at once. Only for people who can read the ticket; never in the event
store. The ticket shows «Bob está editando · Ana también lo está viendo»
above its title; editing means a ticket or comment form is open or a
comment is being written.

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

libs/api/tracker/presenters/src/lib/graphql/issue.resolver.ts

@@ -17,6 +17,7 @@ import {
   BlockersService,
   CommentsService,
   IssuesService,
+  PresenceService,
   WorkflowsService,
 } from '@task-stream/api/tracker/application';
 import {
@@ -48,6 +49,7 @@ import {
   IssueGql,
   IssuePageGql,
   IssueParentGql,
+  PresenceGql,
 } from './types';
 
 @Resolver(() => IssueGql)
@@ -57,8 +59,30 @@ export class IssueResolver {
     private readonly commentsService: CommentsService,
     private readonly workflows: WorkflowsService,
     private readonly blockers: BlockersService,
+    private readonly presence: PresenceService,
   ) {}
 
+  @Mutation(() => [PresenceGql], {
+    description:
+      'I am on this ticket (send every ~10 s while the page is open): answers who else is, the ones editing first',
+  })
+  touchPresence(
+    @CurrentUser() me: User,
+    @Args('issueId', { type: () => ID }) issueId: string,
+    @Args('editing', { defaultValue: false }) editing: boolean,
+  ) {
+    return this.presence.touch({ id: me.id, name: me.name }, issueId, editing);
+  }
+
+  @Mutation(() => Boolean, { description: "I left this ticket's page" })
+  async leavePresence(
+    @CurrentUser() me: User,
+    @Args('issueId', { type: () => ID }) issueId: string,
+  ) {
+    await this.presence.leave(me.id, issueId);
+    return true;
+  }
+
   @OptionalAuth()
   @Query(() => IssueGql)
   issue(

libs/api/tracker/presenters/src/lib/graphql/types.ts

@@ -1063,3 +1063,13 @@ export class ProjectInsightsGql {
   })
   fields!: FieldBreakdownGql[];
 }
+
+@ObjectType('Presence', {
+  description: 'Someone on a ticket right now (heartbeat in the last 30 s)',
+})
+export class PresenceGql {
+  @Field(() => UserRefGql) user!: UserRefGql;
+  @Field({ description: 'Editing the ticket or writing a comment' })
+  editing!: boolean;
+  @Field({ description: 'Last heartbeat' }) at!: string;
+}

libs/api/tracker/presenters/src/lib/http/dto/requests.dto.ts

@@ -1188,6 +1188,16 @@ export class SetIssueParentDto {
   parent!: string | null;
 }
 
+export class PresenceBodyDto {
+  @ApiPropertyOptional({
+    default: false,
+    description: 'Editing the ticket or writing a comment',
+  })
+  @IsOptional()
+  @IsBoolean()
+  editing = false;
+}
+
 export class ChecklistItemBodyDto {
   @ApiProperty({ example: 'Actualizar el changelog', maxLength: 300 })
   @IsString()

libs/api/tracker/presenters/src/lib/http/dto/responses.dto.ts

@@ -764,6 +764,14 @@ export class ProjectStatsDto {
   byAssignee!: CountByAssigneeDto[];
 }
 
+export class PresenceDto {
+  @ApiProperty({ type: UserRefDto }) user!: UserRefDto;
+  @ApiProperty({ description: 'Editing the ticket or writing a comment' })
+  editing!: boolean;
+  @ApiProperty({ format: 'date-time', description: 'Last heartbeat' })
+  at!: string;
+}
+
 export class ActivityDto {
   @ApiProperty() id!: string;
   @ApiProperty({ example: 'IssueStatusChanged' }) type!: string;

libs/api/tracker/presenters/src/lib/http/issues.controller.ts

@@ -13,6 +13,7 @@ import {
 } from '@nestjs/common';
 import {
   ApiCreatedResponse,
+  ApiNoContentResponse,
   ApiOkResponse,
   ApiOperation,
   ApiParam,
@@ -31,6 +32,7 @@ import {
 import {
   CommentsService,
   IssuesService,
+  PresenceService,
 } from '@task-stream/api/tracker/application';
 import { IssueLinkType } from '@task-stream/api/tracker/domain';
 import { withoutNulls } from '../common/issue-input';
@@ -42,6 +44,7 @@ import {
   AddCommentDto,
   CreateIssueDto,
   IssueSearchQueryDto,
+  PresenceBodyDto,
   LinkIssueDto,
   LinkTypeParamDto,
   MyIssuesQueryDto,
@@ -60,6 +63,7 @@ import {
   EpicDto,
   IssueDto,
   IssuePageDto,
+  PresenceDto,
 } from './dto/responses.dto';
 import { viewerOf } from '../common/viewer';
 import { toBulkChange } from '../common/bulk';
@@ -85,8 +89,40 @@ export class IssuesController {
     private readonly issues: IssuesService,
     private readonly comments: CommentsService,
     private readonly refs: Refs,
+    private readonly presence: PresenceService,
   ) {}
 
+  @Put('issues/:issue/presence')
+  @ISSUE
+  @ApiOperation({
+    summary: 'I am on this ticket (heartbeat)',
+    description:
+      'Send it every ~10 s while the page is open; entries fade after 30 s without one. Answers who else is there, the ones editing first.',
+  })
+  @ApiOkResponse({ type: [PresenceDto] })
+  @ApiReadErrors()
+  async touchPresence(
+    @CurrentUser() me: User,
+    @Param('issue') issue: string,
+    @Body() body: PresenceBodyDto,
+  ) {
+    return this.presence.touch(
+      { id: me.id, name: me.name },
+      await this.refs.issueId(me.id, issue),
+      body.editing,
+    );
+  }
+
+  @Delete('issues/:issue/presence')
+  @HttpCode(204)
+  @ISSUE
+  @ApiOperation({ summary: "I left this ticket's page" })
+  @ApiNoContentResponse()
+  @ApiReadErrors()
+  async leavePresence(@CurrentUser() me: User, @Param('issue') issue: string) {
+    await this.presence.leave(me.id, await this.refs.issueId(me.id, issue));
+  }
+
   @Put('issues/:issue/watch')
   @ISSUE
   @ApiOperation({