feat: initial CR-Core library (team + player + command framework)

Pure Maven library for CR Minecraft game plugins, targeting Paper 1.16.5.

Common abstractions (fr.luc.crcore.common): Identifiable, Named, ScoreHolder,
AbstractEntity, Repository<T>.

Team domain (fr.luc.crcore.team): Team entity with name/tag/color/leader/
visibility (PUBLIC|PRIVATE)/members/scores/spawn point, TeamMember,
TeamRole/TeamColor/TeamVisibility enums, TeamRanking record, TeamService with
overridable hooks (factories, validations, lifecycle events), in-memory
repository, dedicated exception hierarchy.

Player domain (fr.luc.crcore.player): PlayerProfile with named scores per
player, PlayerProfileService with auto-creation, individual rankings,
exception hierarchy. Both Team and PlayerProfile implement ScoreHolder.

Command framework (fr.luc.crcore.command): Command interface,
AbstractCommand base, BaseCommand (CommandExecutor + TabCompleter), SubCommand,
CommandContext, CommandResult, ArgumentType<T> + ArgumentTypes catalogue
(STRING, INTEGER, DOUBLE, BOOLEAN, ONLINE_PLAYER, enumOf, choice).

Docs (docs/) is the single source of truth: README, setup, features,
decisions log, and 6 PlantUML diagrams (team class/sequence/activity/join,
player class, command class).

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

docs/diagrams/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