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/DICT.md

@@ -0,0 +1,25 @@
+# Domain Dictionary (DICT)
+
+Cite in `CrossReference` only if the instance exists (`new-artifact.sh` checks this for you):
+
+- **BC** — The business goals the vocabulary serves
+- **SA** — The Product Owner (and other business stakeholders) whose terms are recorded
+- **DM** — Concepts whose PO terms are recorded
+
+## Required sections (after Metadata / Version History)
+
+1. **Purpose and Scope** — the PO language (from the registry's `Languages`
+   section) and what the dictionary covers.
+2. **Dictionary** — one row per term:
+   `PO term | Language | IT term | Definition | Used as PO term in | Used as IT term in`.
+   The definition is written in the PO language. "Used as PO term in" and
+   "Used as IT term in" list artifact types (for example `DM` and `OC, SD,
+   DCD, ERD`).
+3. **Rules** — the register split (PO term in the Domain Model, use cases and
+   user stories; IT term in the Operation Contract, Sequence Diagram, Design
+   Class Diagram and ERD) and one IT term per PO term.
+
+Keep the dictionary in step with the Domain Model: a new concept gets a row
+in the same change. When the PO language is English, the PO and IT columns can
+still differ (a business word against a technical one); keep the file anyway
+when the two registers use different words.