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/templates/RC.md

@@ -0,0 +1,39 @@
+# @TITLE@
+
+## Metadata
+| Key | Value |
+| --- | --- |
+| ID | @ID@ |
+| CrossReference | @CROSSREF@ |
+
+## Version History
+| Date | Status | Author | Reviewer | Change | Commit |
+| --- | --- | --- | --- | --- | --- |
+| @DATE@ | Accepted | @AUTHOR@ | <reviewer S-ID> | Initial version | pending |
+
+---
+
+## Artifact Under Review
+
+- Instance reviewed: [<INSTANCE-ID>]
+- Checklist used: [<QC-ID>] (`QC-<short-name>-<version>`, e.g. `QC-BC-001`)
+
+## Checklist Results
+
+| # | Criterion | Status | Evidence/Notes |
+| --- | --- | --- | --- |
+| 1 | <criterion copied from the QC checklist> | Pass/Fail/N-A | |
+
+## Overall Verdict
+
+<Go / Go-with-conditions / No-Go> — <rationale>
+
+## Action Items
+
+| Action | Owner | Due |
+| --- | --- | --- |
+| <action> | <stakeholder ID, e.g. S07> | <date> |
+
+---
+
+@LINKS@