feat(aidd-pm): add a story-map route to User Stories

Start at the aidd-pm:02-user-stories map route and trace how configured support supplies and persists existing Stories. Done means the route confirms an ordered backbone and named value slices, preserves references without changing Stories, and verifies persisted readback with complete, non-duplicated scope accounting.

Problem

Existing User Stories can be ordered, but the framework has no product-level view that groups those Stories under ordered user activities and makes the smallest coherent value slice visible.

A Story Map is a projection of an existing Story set: its backbone is the user activities, and its bands show value slices. It must remain independent of any particular tracker, sprint, milestone, calendar, or release mechanism.

Decision

Do not add a separate story-map skill. Add a map route to aidd-pm:02-user-stories.

The concern belongs there: User Stories already own their vertical slicing, ordering, relations, and persistence. A Story Map adds the complementary horizontal organisation of the same Stories. A new skill would add another entry point and lifecycle without evidence that maps need to be independently managed as a product artifact.

aidd-pm:07-epic is not the owner: its contract deliberately stays at outcome level and does not propose child slices. Product Brief, Three Amigos, and the backlog orchestrator respectively frame opportunities, assess existing artifacts, and coordinate work; none owns this Story projection.

Scope

• Add a map route to aidd-pm:02-user-stories.
• Take an explicit, existing Story scope from the project’s configured support.
• Propose an ordered backbone of user activities from that Story scope, then obtain the user’s confirmation before persisting.
• Persist a Story Map on the selected support when authorised. It references Stories; it never copies, creates, rewrites, transitions, or moves them.
• Organise the selected Stories into named value slices. A slice is a product-value grouping, not a GitHub milestone, sprint, calendar period, or release implementation by default.
• Keep any projection to a tracker, roadmap, milestone, or release process outside this route unless a future, explicit integration defines it.

Terminology

slice in the existing User Stories route remains a vertical decomposition into independently valuable Stories.

The map route performs the complementary horizontal organisation:

• backbone: ordered user activities;
• value slice: a coherent band of referenced Stories;
• unallocated: a Story in the selected scope that is deliberately not assigned to a value slice.

Acceptance criteria

• A caller supplies existing Stories from its configured support; the route never invents or redrafts a Story.
• The result contains a confirmed ordered backbone and named value slices.
• Each selected Story is referenced at most once in a value slice, or is explicitly unallocated.
• The map owns membership references; it does not add release, slice, or duplicate relation fields to Stories.
• The route is support-agnostic and does not infer a tracker, milestone, sprint, or release integration.
• A persisted map is read back and verified: every reference resolves, no Story is duplicated, and the requested scope is accounted for.

Extraction threshold

A future standalone Story Map skill is justified only if maps acquire an independent lifecycle: for example, several maps maintained separately, scenario comparison, map versioning, cross-backlog composition, or dedicated relationships and transitions. Until then, a route in 02-user-stories is the smallest coherent surface.