Model Spell a Word: use case diagram, user story, use case and SSD

Task: MIL-002#1
Refs #8

docs/use-case-diagram.md

@@ -0,0 +1,58 @@
+# Use Case Diagram
+
+## Metadata
+| Key | Value |
+| --- | --- |
+| ID | UCD-001 |
+| CrossReference | [SA-001], [BC-001], [US-001], [UC-001] |
+| Language | en |
+| Domain | it |
+
+## Version History
+| Date | Status | Author | Reviewer | Change | Commit |
+| --- | --- | --- | --- | --- | --- |
+| 2026-10-13 | Accepted | Jens Tirsvad Nielsen | AI as stand-in for S01 | Initial version, reviewed in RC-010 | pending |
+
+---
+
+## Purpose and Scope
+
+The boundary is the NATO alphabet console tool. One actor, the User, asks the tool to spell a word. Everything outside the console program (the course platform, the git host, the wiki) is outside the boundary.
+
+## Diagram
+
+```plantuml
+@startuml
+left to right direction
+actor "User" <<Actor>> as U
+rectangle "NATO alphabet tool" <<System>> {
+  usecase "Spell a Word" as UC1
+}
+U --> UC1
+@enduml
+```
+
+## Actor Table
+
+| Actor | Stereotype | Stakeholder ID (SA) | Goals (use cases) |
+| --- | --- | --- | --- |
+| User | `<<Actor>>` | S01, S02 | Spell a Word |
+
+## Use Case Table
+
+| Use Case | Actor(s) | Goal |
+| --- | --- | --- |
+| Spell a Word | User | Get the NATO code word of each letter of a word, so the word can be spelled out over the phone |
+
+## Relationships
+
+| From | Relationship (`<<include>>` / `<<extend>>`) | To | Justification |
+| --- | --- | --- | --- |
+| None | - | None | A single use case has no include or extend relationship |
+
+---
+
+[SA-001]: ./stakeholder-analysis.md
+[BC-001]: ./business-case.md
+[US-001]: ./user-stories.md
+[UC-001]: ./uc-001/uc.md