Buy fleet berths with Fleet Offices

#219: fleet capacity is a built, supplied thing rather than a researched
one. The eight fleet-size doctrines are gone; capacity is one berth free
plus one per Fleet Office standing. An office charges every 25s for the
vessel in its berth, priced off that vessel's own build cost so an expensive
hull is expensive to keep, and drawn from its own store the way a gas burner
draws gas. An office that cannot pay goes dark, its vessel is scuttled, and
the player is told through the same queue quest lines use - which reaches
them on a planet surface too.

An empty berth is idle rather than starved: an office is only failing while
there is something in it to fail, and holding it disabled would leave a
berth that could never be crewed and so could never be paid for again.

Ships have no hit points and a shield absorbs a hit wholesale, so the lost
vessel is scuttled rather than damaged - otherwise a shielded hull would
survive its own eviction.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019AJMdB7iuHuLFZM1aBu3GD

tests/test_wave_system.gd

@@ -126,20 +126,22 @@ func _state_cases() -> bool:
 	var patient: int = game_state.wave_number
 	for wave in [1, 5, 20, 60]:
 		game_state.wave_number = wave
-		for size in range(1, GameState.BASE_FLEET_SIZE + 1):
+		for size in range(1, 4):
 			for id in game_state.wave_composition(size):
 				if id != "chaser":
 					game_state.wave_number = patient
 					return _fail("wave %d against a fleet of %d fields a %s" \
 						% [wave, size, id])
 	game_state.wave_number = patient
-	print("a fleet of %d or fewer meets chasers only, at every wave number" \
-		% GameState.BASE_FLEET_SIZE)
+	print("a fleet of 3 or fewer meets chasers only, at every wave number")
 
 	# And each vessel past the starting three opens exactly one more kind, so
 	# the ramp is progressive rather than a cliff.
+	# Explicit sizes rather than BASE_FLEET_SIZE + n: #219 moved the starting
+	# capacity to 1, and this is about the roster's own thresholds (4, 5, 6),
+	# not about where the fleet happens to begin.
 	var previous_kinds: int = 1
-	for size in range(GameState.BASE_FLEET_SIZE, GameState.BASE_FLEET_SIZE + 4):
+	for size in range(3, 8):
 		var kinds_here: Dictionary = {}
 		for id in game_state.wave_composition(size):
 			kinds_here[id] = true