feat(progression): XP, niveaux et popups flottants (+N XP)

Nouvel autoload PlayerProgress qui gagne de l'XP sur:
- cassage de blocs (gain variable selon le type: perle, épave, coral > sand)
- collecte de perles (+25)
- crafting (+10)
- paliers de profondeur atteints (+20 à 10/25/50/75/100m)

HUD: barre XP + label niveau en bas centre, bannière "NIVEAU X" au level-up
(son bulle + fade). Popup 3D "+N XP" spawn au point d'action.

Boucle court-terme dopamine: chaque action = feedback visuel immédiat.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scripts/progression/PlayerProgress.gd

@@ -0,0 +1,67 @@
+extends Node
+
+signal xp_gained(amount: int, source: String, world_position: Vector3)
+signal xp_changed(current_xp: int, xp_for_next: int, level: int)
+signal level_up(new_level: int)
+
+const XP_BREAK_DEFAULT: int = 2
+const XP_BREAK_BY_BLOCK: Dictionary = {
+	2: 1,    # sand
+	3: 2,    # rock
+	4: 5,    # coral rouge
+	5: 5,    # coral bleu
+	6: 1,    # kelp
+	7: 8,    # epave
+	8: 3,    # glace
+}
+const XP_PEARL: int = 25
+const XP_CRAFT: int = 10
+const XP_ECHOLOCATE: int = 3
+const XP_KILL_HOSTILE: int = 15
+const XP_DEPTH_MILESTONE: int = 20
+
+var current_xp: int = 0
+var level: int = 1
+
+var _reached_depths: Array[int] = []
+
+
+func _ready() -> void:
+	emit_state()
+
+
+func xp_for_level(lv: int) -> int:
+	return 50 + (lv - 1) * 40 + (lv - 1) * (lv - 1) * 10
+
+
+func xp_for_next() -> int:
+	return xp_for_level(level)
+
+
+func award(amount: int, source: String = "", world_pos: Vector3 = Vector3.ZERO) -> void:
+	if amount <= 0:
+		return
+	current_xp += amount
+	xp_gained.emit(amount, source, world_pos)
+	while current_xp >= xp_for_next():
+		current_xp -= xp_for_next()
+		level += 1
+		level_up.emit(level)
+	emit_state()
+
+
+func award_block_break(block_id: int, world_pos: Vector3) -> void:
+	var gain: int = XP_BREAK_BY_BLOCK.get(block_id, XP_BREAK_DEFAULT)
+	award(gain, "bloc", world_pos)
+
+
+func emit_state() -> void:
+	xp_changed.emit(current_xp, xp_for_next(), level)
+
+
+func note_depth(depth_m: int) -> void:
+	var milestones: Array[int] = [10, 25, 50, 75, 100]
+	for m: int in milestones:
+		if depth_m >= m and not _reached_depths.has(m):
+			_reached_depths.append(m)
+			award(XP_DEPTH_MILESTONE, "profondeur %dm" % m, Vector3.ZERO)

scripts/progression/XpPopup.gd

@@ -0,0 +1,42 @@
+extends Node3D
+
+var _label: Label3D = null
+var _elapsed: float = 0.0
+var _lifetime: float = 1.4
+var _drift: float = 1.6
+
+
+static func spawn(parent: Node, text: String, world_pos: Vector3, color: Color = Color(1.0, 0.9, 0.2)) -> void:
+	var popup := Node3D.new()
+	popup.set_script(load("res://scripts/progression/XpPopup.gd"))
+	parent.add_child(popup)
+	popup.global_position = world_pos
+	popup.configure(text, color)
+
+
+func configure(text: String, color: Color) -> void:
+	_label = Label3D.new()
+	_label.text = text
+	_label.font_size = 54
+	_label.outline_size = 6
+	_label.modulate = color
+	_label.billboard = BaseMaterial3D.BILLBOARD_ENABLED
+	_label.no_depth_test = true
+	_label.render_priority = 4
+	_label.pixel_size = 0.008
+	add_child(_label)
+
+
+func _process(delta: float) -> void:
+	_elapsed += delta
+	var t: float = _elapsed / _lifetime
+	position.y += _drift * delta
+	if _label != null:
+		var alpha: float = 1.0 - clampf(t, 0.0, 1.0)
+		var c: Color = _label.modulate
+		c.a = alpha
+		_label.modulate = c
+		var scale_factor: float = 1.0 + (1.0 - alpha) * 0.4
+		_label.scale = Vector3.ONE * scale_factor
+	if _elapsed >= _lifetime:
+		queue_free()