fix(multiplayer): validate ranked season expiry

Game/scripts/ranked_profile_state.gd

@@ -39,13 +39,25 @@ func apply(payload: Dictionary) -> bool:
 	provisional = bool(payload["provisional"])
 	season_id = String(payload.get("season_id", ""))
 	season_ends_at_unix = 0
-	if payload.has("season_ends_at") and payload["season_ends_at"] is String and not String(payload["season_ends_at"]).is_empty():
-		season_ends_at_unix = maxi(0, int(Time.get_unix_time_from_datetime_string(String(payload["season_ends_at"]))))
+	if payload.has("season_ends_at"):
+		if not payload["season_ends_at"] is String or not is_valid_season_timestamp(String(payload["season_ends_at"])):
+			return _reject("Profile response contains invalid season expiry")
+		var parsed_season_end := Time.get_unix_time_from_datetime_string(String(payload["season_ends_at"]))
+		if parsed_season_end < 0:
+			return _reject("Profile response contains invalid season expiry")
+		season_ends_at_unix = int(parsed_season_end)
 	available = true
 	error_message = ""
 	return true
 
 
+static func is_valid_season_timestamp(value: String) -> bool:
+	if value.is_empty():
+		return false
+	var timestamp_pattern := RegEx.create_from_string("^\\d{4}-\\d{2}-\\d{2}T\\d{2}:\\d{2}:\\d{2}(?:\\.\\d+)?(?:Z|[+-]\\d{2}:\\d{2})$")
+	return timestamp_pattern.search(value) != null
+
+
 func set_error(reason: String) -> void:
 	available = false
 	error_message = reason

Game/tests/cases/test_control_plane_client.gd

@@ -163,3 +163,5 @@ func test_ranked_profile_projects_and_bounds_season_countdown() -> void:
 	assert_true(profile.apply({"rating": 1500.0, "rd": 200.0, "volatility": 0.06, "ranked_games": 10, "tier": "GOLD", "provisional": false, "season_id": "s1", "season_ends_at": "1970-01-03T00:00:00Z"}), "season end applies")
 	assert_true(profile.display_text(1000).contains("Season ends in 2d"), "countdown rounds up remaining season time")
 	assert_true(profile.display_text(300000).contains("Season ends in 0d"), "expired season countdown is clamped")
+	assert_true(not profile.apply({"rating": 1500.0, "rd": 200.0, "volatility": 0.06, "ranked_games": 10, "tier": "GOLD", "provisional": false, "season_ends_at": "not-a-timestamp"}), "malformed season expiry is rejected")
+	assert_true(not profile.apply({"rating": 1500.0, "rd": 200.0, "volatility": 0.06, "ranked_games": 10, "tier": "GOLD", "provisional": false, "season_ends_at": 123}), "non-string season expiry is rejected")

multiplayer-next.md

@@ -1577,6 +1577,8 @@ Assignment expiry validation now fails closed on malformed non-empty timestamps
 
 MatchNet join-authorisation admission now applies the same expiry format guard before parsing signed roster claims, closing the malformed-expiry gap at the transport handshake boundary.
 
+Ranked profile season metadata now validates optional expiry type and RFC3339 format before deriving the UI countdown, rejecting malformed server projections instead of silently displaying a profile without season context.
+
 Signed MatchNet claims now also require exact JSON string/integer types for every identity, protocol, expiry, slot, team, and generation field; string-number coercion is rejected before canonical signature verification.
 
 Presentation progress: a shared `Game/themes/cosmic_clash_theme.tres` now gives the menu, lobby, matchmaking, and settings surfaces consistent button, input, option, and label styling. The custom-font portion of `TODO.md` remains open until a distributable font asset is selected.