openup: doc restructure - template alignment + design sequences (non-PSP)

Align the OpenUP markdown set to the blank templates (process-data repo,
templates/openup/) per BUILD-CHECKLIST 7. Scenario step text unchanged;
the EA model needs no change (brief descriptions already live in the
model's UC/actor notes).

- vision.md: positioning tables, stakeholder summary, user environment,
  needs-and-features table (R1/R2), other product requirements
- use-case-model.md: per-UC specification sections (brief description,
  actor descriptions, named alternative/exception subsections with
  numbered steps, post-conditions, special requirements)
- supplementary-specifications.md: category tables with priority and
  use-case columns + reverse coverage matrix; IDs unchanged
- test/quality-check-procedure.md: migrated from Joplin (single content
  home); stale open items marked resolved (WI-1/WI-2)
- analysis-design/sequences/: 12 PlantUML design sequences (lifelines =
  analysis classes, messages = design elements; per the PlantUML layout
  style guide) + PNG renders; embedded in Architecture Notebook 9.3
- Joplin consolidated: project content notes deleted (all live in
  docs/game + docs/openup); Joplin keeps the status note only

docs/openup/analysis-design/sequences/uc-01-register.puml

@@ -0,0 +1,23 @@
+@startuml uc-01-register
+autonumber
+title UC-01 Register Account (design sequence)
+actor Guest
+participant "AuthBoundary\n«POST /api/auth/register»" as boundary <<boundary>>
+participant "AccountRegistry\nsb-api::routes::register" as control <<control>>
+participant "UserAccount\nsb-shared::user::User" as entity <<entity>>
+
+== Register ==
+Guest -> boundary : name (3-32), password (>= 6)
+boundary -> control : register(name, password)
+alt name invalid / password too short
+  control --> boundary : 400
+else name taken
+  control --> boundary : 409 CONFLICT
+else valid
+  control -> entity : hash password (argon2, sb-auth)
+  control -> entity : assign player role + next id
+  control -> entity : persist (sb-db)
+  control --> boundary : JWT HS256 (player role)
+  boundary --> Guest : {token, user_id, name, role}
+end
+@enduml