Add planning baseline: BC, SA, PP and two gateways

Create the Business Case, Stakeholder Analysis (S01 course participant,
S02 Udemy coursists, S03 GitHub viewers), Project Plan and the milestone
documents MIL-001 (project setup, 6 tasks) and MIL-002 (game
implementation, 8 tasks) for the console Blackjack game.

Register PP and MIL in the artifact registry, set the PO language to en,
and link the synced Gitea milestones in the Gateway Schedule.

Refs #1
Refs #2
Refs #3
Refs #4
Refs #5
Refs #6
Refs #7
Refs #8
Refs #9
Refs #10
Refs #11
Refs #12
Refs #13
Refs #14

.agents/skills/artifact/references/BMC.md

@@ -0,0 +1,21 @@
+# Business Model Canvas (BMC)
+
+Cite in `CrossReference` only if the instance exists (`new-artifact.sh` checks this for you):
+
+- **BC** — Objectives the canvas operationalizes; cost/revenue must agree with its Cost–Benefit Assessment
+- **SA** — Value Propositions, Customer Segments, Channels — cite S-IDs
+- **BPMN** — Key Activities — cite the process that realizes them
+- **KPI** — Measures of value proposition / revenue — cite KPI IDs
+
+## Required sections (after Metadata / Version History)
+
+1. **Purpose / Scope** — one paragraph.
+2. **Canvas** — all 9 building blocks populated, none empty: Key Partners,
+   Key Activities, Key Resources, Value Propositions, Customer
+   Relationships, Channels, Customer Segments, Cost Structure, Revenue
+   Streams. Must stay reviewable as a single, concise overview.
+3. **Assumptions** — explicit and testable (how would we know it is wrong?).
+4. **Consistency Check** — Revenue Streams vs Cost Structure agree;
+   Segments/Channels match stakeholder groups from `SA`.
+
+Cite Business Case objectives (`[BC-001]`) instead of restating them.