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/player/player-class-diagram.puml

@@ -0,0 +1,110 @@
+@startuml player-class-diagram
+title CR-Core — Player domain (class diagram)
+
+skinparam classAttributeIconSize 0
+hide empty members
+
+' === Common abstractions ===
+
+package "fr.luc.crcore.util.common" {
+
+  interface Identifiable {
+    + getId(): UUID
+  }
+
+  interface ScoreHolder {
+    + getScore(name): int
+    + hasScore(name): boolean
+    + getScores(): Map<String, Integer>
+    + getTotalScore(): int
+    + addScore(name, delta): int
+    + setScore(name, value): int
+    + resetScore(name): boolean
+    + resetAllScores(): void
+  }
+
+  abstract class AbstractEntity {
+    - id: UUID
+    + getId(): UUID
+  }
+
+  interface "Repository<T extends Identifiable>" as Repository {
+    + save(entity: T): T
+    + findById(id): Optional<T>
+    + findAll(): Collection<T>
+    + delete(id): boolean
+  }
+
+  AbstractEntity ..|> Identifiable
+}
+
+' === Player domain ===
+
+package "fr.luc.crcore.features.player" {
+
+  class PlayerProfile {
+    - scores: Map<String, Integer>
+    + PlayerProfile(playerId: UUID)
+    + getPlayerId(): UUID
+  }
+
+  class PlayerRanking <<record>> {
+    + rank: int
+    + profile: PlayerProfile
+    + score: int
+  }
+
+  interface PlayerProfileRepository
+
+  class InMemoryPlayerProfileRepository {
+    - profiles: Map<UUID, PlayerProfile>
+  }
+
+  interface PlayerProfileService {
+    + getOrCreateProfile(playerId): PlayerProfile
+    + getProfile(playerId): Optional<PlayerProfile>
+    + deleteProfile(playerId): boolean
+    + getAllProfiles(): Collection<PlayerProfile>
+    --
+    + addScore(playerId, name, delta): int
+    + setScore(playerId, name, value): int
+    + getScore(playerId, name): int
+    + resetScore(playerId, name): boolean
+    + resetAllScores(playerId): void
+    --
+    + getRankingByScore(name): List<PlayerRanking>
+    + getGlobalRanking(): List<PlayerRanking>
+    + getTopRankingByScore(name, limit): List<PlayerRanking>
+    + getTopGlobalRanking(limit): List<PlayerRanking>
+  }
+
+  class PlayerProfileServiceImpl {
+    - repository: PlayerProfileRepository
+    --
+    # newProfile(playerId): PlayerProfile
+    # newRanking(rank, profile, score): PlayerRanking
+    # rank(scoreFn): List<PlayerRanking>
+    --
+    # onProfileCreated(profile): void
+    # onProfileDeleted(profile): void
+    # onScoreChanged(profile, name, oldV, newV): void
+  }
+
+  class PlayerException
+  class PlayerProfileNotFoundException
+
+  PlayerProfile --|> AbstractEntity
+  PlayerProfile ..|> ScoreHolder
+  PlayerProfileRepository --|> Repository
+  InMemoryPlayerProfileRepository ..|> PlayerProfileRepository
+  PlayerProfileServiceImpl ..|> PlayerProfileService
+
+  PlayerRanking --> PlayerProfile
+  PlayerProfileServiceImpl o--> PlayerProfileRepository
+  PlayerProfileService ..> PlayerRanking : produces
+
+  PlayerException --|> RuntimeException
+  PlayerProfileNotFoundException --|> PlayerException
+}
+
+@enduml