t_p6_api: build plugin scripting system

- Add PluginBase (plugin_base.gd) — abstract base class with 12 virtual hooks
- Add PluginManifest (plugin_manifest.gd) — custom Resource for plugin metadata
- Add PluginManager (plugin_manager.gd) — autoload singleton: directory scan,
  hook dispatch, lifecycle (load/unload/reload/rescan), cvar integration
- Add hello_world example plugin with all hooks demonstrating usage
- Register PluginManager autoload in project.godot
- Extend rcon_command_handler.gd with 'plugin' subcommand (list/load/unload/
  reload/info/rescan) delegating to PluginManager

server/plugins/hello_world/hello_world.gd

@@ -0,0 +1,104 @@
+## Hello World — Example Server Plugin
+##
+## Demonstrates all available plugin hooks by logging each event.
+## Use this as a template for creating new plugins.
+
+extends PluginBase
+class_name HelloWorldPlugin
+
+# ---------------------------------------------------------------------------
+# Plugin state
+# ---------------------------------------------------------------------------
+var _player_count: int = 0
+var _round_count: int = 0
+var _tick_count: int = 0
+var _start_time: int = 0
+
+# ---------------------------------------------------------------------------
+# Initialization
+# ---------------------------------------------------------------------------
+func _ready() -> void:
+	log_info("Hello World plugin initializing...")
+	_start_time = Time.get_ticks_msec()
+
+func _exit_tree() -> void:
+	log_info("Hello World plugin shutting down. Uptime: %.1f seconds" %
+		[(Time.get_ticks_msec() - _start_time) / 1000.0])
+
+# ---------------------------------------------------------------------------
+# Server lifecycle hooks
+# ---------------------------------------------------------------------------
+func on_server_start() -> void:
+	log_info("on_server_start — Server is now online")
+	_tick_count = 0
+
+func on_server_stop() -> void:
+	log_info("on_server_stop — Server is shutting down")
+
+# ---------------------------------------------------------------------------
+# Map lifecycle hooks
+# ---------------------------------------------------------------------------
+func on_map_start(map_name: String) -> void:
+	log_info("on_map_start — Loading map: %s" % map_name)
+	_player_count = 0
+	_round_count = 0
+
+func on_map_end(map_name: String) -> void:
+	log_info("on_map_end — Map ended: %s (rounds played: %d)" % [map_name, _round_count])
+
+# ---------------------------------------------------------------------------
+# Player hooks
+# ---------------------------------------------------------------------------
+func on_player_connect(id: int, name: String, steam_id: String) -> bool:
+	log_info("on_player_connect — Player connecting: id=%d, name='%s', steam_id=%s" %
+		[id, name, steam_id])
+	# Return true to allow connection
+	return true
+
+func on_player_disconnect(id: int, reason: String) -> void:
+	log_info("on_player_disconnect — Player disconnected: id=%d, reason='%s'" %
+		[id, reason])
+
+func on_player_say(id: int, msg: String) -> bool:
+	log_info("on_player_say — Player %d says: \"%s\"" % [id, msg])
+	# Return true to let the message through
+	return true
+
+func on_player_spawn(id: int) -> void:
+	_player_count += 1
+	log_info("on_player_spawn — Player %d spawned (total spawns: %d)" %
+		[id, _player_count])
+
+func on_player_killed(victim: int, killer: int, weapon: String) -> void:
+	var desc: String
+	if victim == killer:
+		desc = "suicide"
+	else:
+		desc = "killed by %d" % killer
+	log_info("on_player_killed — Player %d %s with '%s'" % [victim, desc, weapon])
+
+# ---------------------------------------------------------------------------
+# Round hooks
+# ---------------------------------------------------------------------------
+func on_round_start(number: int) -> void:
+	_round_count = number
+	log_info("on_round_start — Round %d begins" % number)
+
+func on_round_end(winner_team: int, reason: String) -> void:
+	var team_name: String = "Draw"
+	match winner_team:
+		1:
+			team_name = "Team A"
+		2:
+			team_name = "Team B"
+	log_info("on_round_end — Round %d ended: %s wins (%s)" %
+		[_round_count, team_name, reason])
+
+# ---------------------------------------------------------------------------
+# Per-tick hook
+# ---------------------------------------------------------------------------
+func on_tick(delta: float) -> void:
+	_tick_count += 1
+	# Log only every ~100 ticks to avoid spam (at 128 Hz ≈ every 0.78s)
+	if _tick_count % 100 == 0:
+		log_info("on_tick — Tick %d (delta=%.4f)" % [_tick_count, delta])

server/plugins/hello_world/plugin.tres

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+[gd_resource type="Resource" format=3]
+
+[ext_resource type="Script" path="res://server/scripts/plugin_api/plugin_manifest.gd" id="1_plugin_manifest"]
+
+[resource]
+script = ExtResource("1_plugin_manifest")
+name = "Hello World"
+version = "1.0.0"
+author = "Tactical Shooter Team"
+script_path = "hello_world.gd"
+enabled = true
+min_api_version = "1.0.0"
+max_api_version = ""
+metadata = {
+	"description": "Example plugin that logs all server events",
+	"url": "https://gitea.ourpad.casa/shawn/tactical-shooter"
+}