Expand TODO.md with player registration and session management details.

TODO.md

@@ -14,6 +14,7 @@ A Minecraft survival/PvP plugin with configurable loot, shrinking world border,
 - [Commands](#-commands)
 - [Stats System](#-stats-system)
 - [Configuration](#-configuration)
+- [Player Registration](#-player-registration--session-management)
 
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@@ -88,6 +89,55 @@ A Minecraft survival/PvP plugin with configurable loot, shrinking world border,
 
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+## 👥 Player Registration & Session Management
+
+### Registration
+- [ ] Expose a command (e.g. `/hg join <player>`) callable by other plugins/console to register a player into the upcoming round
+- [ ] Maintain a registered player list per round (separate from online players)
+- [ ] Reject registration if round is already ACTIVE or past COUNTDOWN
+- [ ] Confirm registration with a chat message to the player: `"You have been entered into the round!"`
+- [ ] Allow `/hg leave <player>` to remove a player before the round starts
+- [ ] Allow `/hg kick <player>` (admin) to force-remove a player mid-round (counts as death/DNF, no kill credit)
+
+### Player States
+Track each registered player in one of these states:
+- [ ] `REGISTERED` — signed up, round not yet started
+- [ ] `ALIVE` — actively in the round
+- [ ] `DEAD` — eliminated, waiting in the safe room
+- [ ] `DISCONNECTED` — left the server mid-round
+- [ ] `SPECTATING` — admin/non-participant observer
+
+### Disconnect Handling
+- [ ] On disconnect during COUNTDOWN: remove from round, free their spawn slot
+- [ ] On disconnect during ACTIVE round: treat as death (no kill credit), teleport handling skipped since they're offline
+- [ ] Store disconnect state so if they reconnect before round ends, they are placed in the safe room (not back into the game)
+- [ ] On reconnect mid-round: teleport to safe room, restore DEAD state, notify them the round is ongoing
+- [ ] On reconnect after round ends: restore their normal state
+
+### Join Game Handling
+- [ ] On registration: set player gamemode survival
+- [ ] Teleport player to a configurable lobby/waiting area within the event world on registration
+- [ ] Assign spawn points randomly from the available pool at countdown start — no two players share a point
+- [ ] Teleport all REGISTERED players to their assigned spawn points when countdown begins
+- [ ] Notify player they joined the game
+
+### Safe Room
+- [ ] Command to re-teleport all players not in the game to the safe room
+- [ ] Configurable safe room location (world, x, y, z, yaw, pitch) in config
+- [ ] Teleport eliminated players to safe room immediately on death
+- [ ] Teleport disconnected players to safe room on reconnect (if round still active)
+- [ ] Players in safe room: no PvP, no hunger, no fall damage
+- [ ] Optionally show a live scoreboard or action bar in the safe room (remaining players, kills leaderboard)
+- [ ] Teleport all players out of safe room to a configurable post-round location when round ends
+
+### Round Cleanup
+- [ ] On round end: clear all player states
+- [ ] Restore player inventory, gamemode, health, hunger, potion effects to pre-round state (or a clean default)
+- [ ] Clear any active boss bars, action bars, speed effects from all participants
+- [ ] Reset registered player list ready for next round
+
+---
+
 ## 🧭 Commands
 
 ### `/hg stuck`