feat: sprints with burndown and carry-over

Plan sprints with dates and a goal, run one at a time per project, and
put tickets in them from the ticket page. The Sprints tab follows the one
under way with its progress and a burndown in tickets or points against
the ideal line. Closing a sprint sends what was left to the next one or
back to the backlog; the board can be filtered by sprint.

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

libs/api/tracker/application/src/lib/commands/sprint.commands.ts

@@ -0,0 +1,85 @@
+import { Command } from '@nestjs/cqrs';
+import { SprintDetails } from '@task-stream/api/tracker/domain';
+import { CommandResult } from './command-result';
+
+export class CreateSprintCommand extends Command<CommandResult> {
+  constructor(
+    public readonly actorId: string,
+    public readonly projectId: string,
+    public readonly name: string,
+    public readonly startDate: string,
+    public readonly endDate: string,
+    public readonly goal: string | null = null,
+  ) {
+    super();
+  }
+}
+
+export class UpdateSprintCommand extends Command<CommandResult> {
+  constructor(
+    public readonly actorId: string,
+    public readonly sprintId: string,
+    public readonly changes: SprintDetails,
+  ) {
+    super();
+  }
+}
+
+export class StartSprintCommand extends Command<CommandResult> {
+  constructor(
+    public readonly actorId: string,
+    public readonly sprintId: string,
+  ) {
+    super();
+  }
+}
+
+/** Ends a sprint; unfinished tickets go to `carryOverTo` (null: backlog). */
+export class CloseSprintCommand extends Command<CommandResult> {
+  constructor(
+    public readonly actorId: string,
+    public readonly sprintId: string,
+    public readonly carryOverTo: string | null,
+  ) {
+    super();
+  }
+}
+
+/** A planned sprint (people), or any sprint of a deleted project (`cascade`, saga). */
+export class DeleteSprintCommand extends Command<CommandResult | void> {
+  constructor(
+    public readonly actorId: string,
+    public readonly sprintId: string,
+    public readonly cascade = false,
+  ) {
+    super();
+  }
+}
+
+/** Puts a ticket in a sprint (null: back to the backlog). */
+export class SetIssueSprintCommand extends Command<CommandResult> {
+  constructor(
+    public readonly actorId: string,
+    public readonly issueId: string,
+    public readonly sprintId: string | null,
+  ) {
+    super();
+  }
+}
+
+/**
+ * Saga only: a sprint closed (or was deleted), so a ticket of it moves to
+ * `toSprintId` (null: backlog). With `onlyUnfinished`, finished ones stay as
+ * the record of what the sprint achieved.
+ */
+export class CarryOverIssueCommand extends Command<void> {
+  constructor(
+    public readonly actorId: string,
+    public readonly issueId: string,
+    public readonly fromSprintId: string,
+    public readonly toSprintId: string | null,
+    public readonly onlyUnfinished: boolean,
+  ) {
+    super();
+  }
+}