#125: slow the prologue down, and give the breach a real black hole

Five things, all of them "this happens too fast or looks too thin".

PACING. Every beat had a completion test that could be satisfied while the
guide was still mid-sentence, which is why everything landed seconds after
the thing before it. Beats now have a FLOOR as well as a deadline - a
minimum length - and a beat whose point is the guide talking will not end
while a line is still on screen. One rule in one place rather than tuning
each condition. The run is 3400px instead of 1500, which at cruise was about
four seconds, and a held line is 6.5s instead of 4.5.

THE CONVOY. Escorts at the four corners of a box, holds packed in the middle
of it, roughly three times the spread of the fleet's own wedge - this is
freight under guard, not a fighting formation. CONVOY and CONVOY_FORMATION
pair index-for-index, which is all it takes for spawn_ships to seat the guns
on the outside, and the test pins that every hold sits further in than the
furthest-out escort.

THE DIALOG. Cut corners, brackets holding the short edges open, a tick strip
along the bottom and a caret in the corner - geometry rather than art, so it
scales with the banner and costs nothing.

THE BREACH. It was a few lines turning around a point. It is now two halves
driven by one number: DimensionalBreach, a growing black hole out in the
world built on BlackHoleVisual's idiom - empty core, counter-rotating arc
segments hotter toward the centre - with infalling streamers it does not
have, because a planet's disc is steady and this one has to say "now"; and
breach.gdshader over the top, bending the ACTUAL SCENE around it. Ships,
rocks and the starfield all get dragged in, which is most of what makes a
hole in space read as a hole rather than as a decal drawn on one.

Inside the horizon the shader samples nothing at all - the same decision
BlackHoleVisual makes, for the same reason: a black hole with something
visible in the middle stops being one.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

ui/BreachOverlay.gd

@@ -0,0 +1,43 @@
+extends ColorRect
+
+# #125: drives breach.gdshader.
+#
+# Lives in the UI layer because it works in SCREEN space - it bends the
+# rendered frame, so it has to be the last thing drawn and it has to cover
+# the whole viewport. The world-space half of the breach (the horizon, the
+# accretion disc, the infalling matter) is DimensionalBreach, a Node2D out
+# in the world; this is only the lens over the top of it.
+#
+# Inert unless something calls set_breach(): the shader is a no-op at zero
+# strength, but a full-screen quad that is never needed is still a full
+# screen of fragment work, so it hides itself instead.
+
+const SHADER_PATH: String = "res://shaders/breach.gdshader"
+
+
+func _ready() -> void:
+	mouse_filter = Control.MOUSE_FILTER_IGNORE
+	visible = false
+	if material == null:
+		var shader_material := ShaderMaterial.new()
+		shader_material.shader = load(SHADER_PATH)
+		material = shader_material
+
+
+func clear_breach() -> void:
+	visible = false
+	if material != null:
+		material.set_shader_parameter("strength", 0.0)
+
+
+# `at` is in SCREEN pixels; the director projects the world point through the
+# camera before calling, because only it knows where the camera is.
+func set_breach(at: Vector2, horizon: float, lens: float, breach_strength: float) -> void:
+	if material == null:
+		return
+	visible = breach_strength > 0.001
+	material.set_shader_parameter("breach_center", at)
+	material.set_shader_parameter("viewport_size", size)
+	material.set_shader_parameter("horizon_radius", horizon)
+	material.set_shader_parameter("lens_radius", maxf(lens, horizon + 1.0))
+	material.set_shader_parameter("strength", clampf(breach_strength, 0.0, 1.0))