Add Pretty Table project: plan, accepted documents and code

Business Case, Stakeholder Analysis, Project Plan and milestone MIL-001
with review records RC-001 to RC-003, then the Python project: PrettyTable
Pokemon table, constants, pytest tests, pyproject.toml, Doxyfile, CI
workflow and README.

Task: MIL-001#1
Task: MIL-001#2
Task: MIL-001#3
Task: MIL-001#4
Task: MIL-001#5
Task: MIL-001#6
Task: MIL-001#7
Task: MIL-001#8

.agents/skills/artifact/references/US.md

@@ -0,0 +1,22 @@
+# User Story (US)
+
+Cite in `CrossReference` only if the instance exists (`new-artifact.sh` checks this for you):
+
+- **UCD** — The story's role must match an actor defined here
+- **UC** — The use case each story traces to
+- **BC** — Objective / epic the story ultimately supports
+- **MIL** — The gateway (epic) each story delivers — one or more stories per gateway
+
+## Required sections (after Metadata / Version History)
+
+1. **Purpose and Scope** — the epic(s) covered.
+2. **Story List** — each story with a stable ID `US-<doc-version>.<NN>` (e.g.
+   `US-001.01`, so it cannot be confused with the document ID `US-001`):
+   - Statement: **As a** `<actor>`, **I want** `<goal>`, **so that**
+     `<benefit>` — one goal per story, no implementation detail.
+   - **Acceptance Criteria** — clear and testable (Given/When/Then works).
+   - **Traces to** — the use case (`UC-…`) or epic it comes from; a gateway
+     (`MIL-…`) is an epic.
+   - **Size** — fits a single iteration.
+3. **INVEST Check** — one line confirming Independent, Negotiable,
+   Valuable, Estimable, Small, Testable (flag any exception with reason).