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.

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.agents/skills/artifact/templates/TRR.md

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+# @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 |
+
+---
+
+## Session
+
+| Item | Value |
+| --- | --- |
+| Training material | [<TRN-ID>] |
+| Date | <date of the session> |
+| Facilitator | <stakeholder ID> |
+| Format and place | <in person / online, where> |
+
+## Attendees and Assessment
+
+| Stakeholder ID (SA) | Attended | Assessment (Pass / Not yet) | Notes |
+| --- | --- | --- | --- |
+| <S-ID> | <Yes / No> | <Pass / Not yet> | |
+
+## Feedback
+
+<What attendees said worked and did not.>
+
+## Follow-ups
+
+| Action | Owner | Due |
+| --- | --- | --- |
+| <action, for example a repeat session or a checklist change> | <stakeholder ID> | <date> |
+
+---
+
+@LINKS@