docs: organize diagrams to mirror code layout (util/ + features/)

Move flat docs/diagrams/*.puml into a hierarchy matching the source
package structure:

  docs/diagrams/
  ├── bootstrap-sequence.puml         (cross-cutting)
  ├── events-diagram.puml             (cross-feature)
  ├── util/
  │   ├── command-class-diagram.puml
  │   ├── database-diagram.puml
  │   ├── messages-class-diagram.puml
  │   ├── broadcasts-class-diagram.puml
  │   └── gui-class-diagram.puml
  └── features/
      ├── team/
      │   ├── team-class-diagram.puml
      │   ├── team-config-class-diagram.puml
      │   ├── builtin-commands-diagram.puml
      │   ├── team-create-sequence.puml
      │   ├── team-create-activity.puml
      │   └── team-join-sequence.puml
      ├── player/
      │   └── player-class-diagram.puml
      └── moderation/
          └── moderation-class-diagram.puml

README.md diagram index split into 4 sections (overview, util,
features/team, features/player, features/moderation) for readability;
all links updated. features.md auto-updated by sed for the new paths.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

docs/diagrams/features/team/team-create-sequence.puml

@@ -0,0 +1,69 @@
+@startuml team-create-sequence
+title CR-Core — Create Team via command framework (sequence diagram)
+
+actor Player
+participant "BaseCommand\n(TeamCommand)" as Base
+participant "SubCommand\n(TeamCreateSub)" as Sub
+participant "TeamService" as Service
+participant "TeamRepository" as Repo
+participant "Team" as Team
+
+Player -> Base : /team create <name> <tag> <color>
+activate Base
+
+Base -> Base : route args[0]="create" → TeamCreateSub
+Base -> Base : check permission + playerOnly
+Base -> Sub : buildContext(sender, label, subArgs)
+activate Sub
+Sub -> Sub : parse name (STRING) / tag (STRING) / color (enumOf TeamColor)
+Sub --> Base : CommandContext
+deactivate Sub
+
+Base -> Sub : execute(ctx)
+activate Sub
+
+Sub -> Service : createTeam(name, tag, color, playerId)
+activate Service
+
+Service -> Service : validateName(name)
+Service -> Repo : findByName(name)
+activate Repo
+Repo --> Service : Optional.empty()
+deactivate Repo
+
+Service -> Service : validateTag(tag)
+Service -> Repo : findByTag(tag)
+activate Repo
+Repo --> Service : Optional.empty()
+deactivate Repo
+
+Service -> Service : validateLeader(playerId)
+Service -> Repo : findByMember(playerId)
+activate Repo
+Repo --> Service : Optional.empty()
+deactivate Repo
+
+Service -> Team : newTeam(UUID.randomUUID(), name, tag, color, playerId, PRIVATE)
+activate Team
+Team -> Team : add newMember(playerId, LEADER)
+Team --> Service : team
+deactivate Team
+
+Service -> Service : onBeforeSave(team)
+Service -> Repo : save(team)
+activate Repo
+Repo --> Service : team
+deactivate Repo
+Service -> Service : onAfterCreate(team)
+
+Service --> Sub : team
+deactivate Service
+
+Sub --> Base : CommandResult.success("Team created")
+deactivate Sub
+
+Base -> Base : handleResult → sender.sendMessage(green text)
+Base --> Player : "Team <name> created"
+deactivate Base
+
+@enduml