fix(api): retry commands that clash with a concurrent write

Services run commands through a CommandRunner that runs one again (up to
5 times, waiting a little longer each time) when its aggregate changed
underneath, e.g. a saga writing to the same ticket. Each command loads its
aggregate fresh and stores its events in one transaction, so a
ConcurrencyError means nothing was stored and running it again is safe.
People no longer get a 409 for it, and the e2e suite stops flaking.

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

libs/api/tracker/application/src/lib/git.service.ts

@@ -1,5 +1,6 @@
+import { CommandRunner } from '@task-stream/api/shared/application';
 import { Injectable } from '@nestjs/common';
-import { CommandBus, QueryBus } from '@nestjs/cqrs';
+import { QueryBus } from '@nestjs/cqrs';
 import { ForbiddenError } from '@task-stream/api/shared/domain';
 import {
   AddGitRepositoryCommand,
@@ -30,7 +31,7 @@ export interface GitDelivery {
 @Injectable()
 export class GitService {
   constructor(
-    private readonly commandBus: CommandBus,
+    private readonly commands: CommandRunner,
     private readonly queryBus: QueryBus,
     private readonly findProjects: FindProjectsRepository,
     private readonly integrations: GitIntegrationsRepository,
@@ -47,7 +48,7 @@ export class GitService {
     projectId: string,
     name: string,
   ): Promise<GitRepository> {
-    return this.commandBus.execute(
+    return this.commands.execute(
       new AddGitRepositoryCommand(actorId, projectId, name),
     );
   }
@@ -57,7 +58,7 @@ export class GitService {
     projectId: string,
     repositoryId: string,
   ): Promise<GitRepository> {
-    return this.commandBus.execute(
+    return this.commands.execute(
       new RotateGitRepositorySecretCommand(actorId, projectId, repositoryId),
     );
   }
@@ -67,7 +68,7 @@ export class GitService {
     projectId: string,
     repositoryId: string,
   ): Promise<void> {
-    return this.commandBus.execute(
+    return this.commands.execute(
       new RemoveGitRepositoryCommand(actorId, projectId, repositoryId),
     );
   }
@@ -104,7 +105,7 @@ export class GitService {
       delivery.body,
     );
     if (!mentions.length) return { recorded: 0 };
-    const recorded: number = await this.commandBus.execute(
+    const recorded: number = await this.commands.execute(
       new RecordGitMentionsCommand(project.id, repository.name, mentions),
     );
     return { recorded };