Plan RepoFoundry: business case, stakeholders, plan, milestones, UC-001

Add the planning baseline for RepoFoundry (create-project.sh), which
creates GitHub and Gitea repositories, a Gitea -> GitHub push mirror and
a local project with the SQA-QC-Framework.

- BC-001 Business Case and SA-001 Stakeholder Analysis (S01, S02, S03)
- PP-001 Project Plan: three phases, 2026-10-05 to 2026-11-13 (proposed)
- MIL-001 Foundation, MIL-002 Repositories and Mirror,
  MIL-003 Scaffold and Release, with 18 task rows
- US-001, UC-001 "Create a new project" and SSD-001
- Registry: PO language en; PP, MIL, US, UC and SSD rows added

Decisions recorded: origin uses HTTPS from GITEA_URL unless the SSH test
on port 10022 passes; S01 and S02 are held by one person for now.

Refs: no issues synced yet (sync-project.sh dry run only)

docs/uc-001/ssd.md

@@ -0,0 +1,50 @@
+# System Sequence Diagram
+
+## Metadata
+| Key | Value |
+| --- | --- |
+| ID | SSD-001 |
+| CrossReference | [UC-001] |
+
+## Version History
+| Date | Status | Author | Reviewer | Change | Commit |
+| --- | --- | --- | --- | --- | --- |
+| 2026-10-05 | Proposed | Jens Tirsvad Nielsen | S02 | Initial version | [9ae0cba] |
+
+---
+
+## Source Use Case
+
+Create a new project ([UC-001]) — scenario: main success scenario
+
+## Diagram
+
+```plantuml
+@startuml
+actor Maintainer as A
+participant ":System" as S
+A -> S : startProjectCreation()
+S --> A : prompts for project details
+A -> S : provideProjectDetails(name, description, visibility, githubOwner, giteaOwner, directory, enablePlanGate)
+S --> A : checks passed
+S --> A : creation summary
+@enduml
+```
+
+## System Operations
+
+| Step | Message | Parameters | Return | Use case step |
+| --- | --- | --- | --- | --- |
+| 1 | startProjectCreation | none | prompts for project details (after configuration and tool checks) | 1, 2 |
+| 2 | provideProjectDetails | name, description, visibility, githubOwner, giteaOwner, directory, enablePlanGate | checks passed, then a creation summary | 3 to 10 |
+
+Steps 4 to 9 are internal to the system, so one operation covers them. A consent question (step 8a, 9a, 9b) is a prompt from the system and is out of scope for this diagram; failure flows are out of scope here.
+
+## Lifecycle Notes
+
+The system is one script run. It starts with the first operation and ends after the summary; nothing persists between runs.
+
+---
+
+[UC-001]: ./uc.md
+[9ae0cba]: https://git.tirsystem.com/TirSystem-BashScript/repo_foundry/commit/9ae0cba306577833480f692c67c0ec327ff2e24e