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/KPI.md

@@ -0,0 +1,20 @@
+# KPI Definitions (KPI)
+
+Cite in `CrossReference` only if the instance exists (`new-artifact.sh` checks this for you):
+
+- **BC** — The Success Criteria row each KPI is aligned to (`[BC-001]`)
+
+## Required sections (after Metadata / Version History)
+
+1. **Purpose** — which Business Case success criteria this document
+   operationalizes.
+2. **KPI Definitions** — one row per KPI: `KPI ID | Name | SMART statement |
+   Baseline | Target | Business Case Success Criterion | Owner | Frequency &
+   Method | Data Source`.
+3. **Thresholds** — per KPI: acceptable / at-risk / failing bounds.
+4. **Reporting** — where results are reported and to whom.
+
+Rules: every KPI is SMART (reject goals/activities like "improve quality");
+baseline *and* target are both present; `Owner` is a stakeholder ID from
+the project's Stakeholder Analysis (e.g. `S07`), never free text; give KPIs stable IDs (`KPI-01`, …) so
+Milestones can cite them.