Fix pivot tap-spam speed exploit (#72)

_finish_pivot_tap() granted a full PIVOT_MIN_STEP rotation on every
button/key release with no rate limit, so tapping fast enough rotated
the formation far beyond PIVOT_SPEED's smooth held-rate cap - well
above what holding the button down can ever produce. Each of those
artificially-frequent re-seats (Fleet.apply_formation()) forced every
ship into a fresh max-speed catch-up dash toward its new slot with no
time to settle between dashes, and since outer-wedge ships swing
further per pivot than inner ones, spamming made them visibly diverge
in speed while each ship's own bounded max_speed made the fleet read
as constantly pinned at its speed ceiling.

Added a per-direction cooldown (the time a genuine hold needs to reach
PIVOT_MIN_STEP on its own) so tap-spam can't out-pace holding the
button. Deliberately NOT shared between CW/CCW: a quick correction tap
the other way right after an overshoot is normal play, and
test_keyboard_input.gd already covers Q and E each independently
producing their own minimum step back-to-back - only repeatedly
re-tapping the SAME direction needed capping.

tests/test_pivot_controls.gd

@@ -5,7 +5,10 @@ extends SceneTree
 # Covers the fleet-pivot buttons:
 #   1. HOLDING one turns the formation continuously, not once per press
 #   2. a brief tap still produces a clear minimum step
-#   3. pivoting works while the fleet is under way, i.e. the new layout
+#   3. immediately repeating a tap grants nothing extra until the cooldown
+#      clears (#72) - spamming taps must never rotate faster than holding
+#      the button would
+#   4. pivoting works while the fleet is under way, i.e. the new layout
 #      survives the joystick's per-frame steering updates instead of being
 #      overwritten by the old offsets
 
@@ -76,6 +79,17 @@ func _process(delta: float) -> bool:
 				quit(1)
 				return true
 
+			# --- #72: spamming taps grants nothing extra during the cooldown ---
+			var before_spam: float = _angle()
+			for i in range(5):
+				controller._finish_pivot_tap(1.0)
+			var spammed: float = absf(angle_difference(before_spam, _angle()))
+			print("5 taps back-to-back -> turned %.4f rad (expected ~0, cooldown not yet cleared)" % spammed)
+			if spammed > 0.001:
+				print("TEST_PIVOT_CONTROLS: FAIL (tap-spam granted rotation during the cooldown)")
+				quit(1)
+				return true
+
 			# --- pivot WHILE the joystick is held -------------------------
 			# Two fingers at once. This is routed through the same raw-touch
 			# path the real device uses, because Godot's Control GUI treats