Skill tree, node-based building animation, bigger UI, and a 19x faster test suite

Gameplay and UI
- Research tree at the mothership gates which structures can be built and
  grants permanent fleet-capacity upgrades (GameState.SKILL_TREE,
  SkillTreeView). Node depth is derived from prerequisites, so the layout
  cannot drift out of step with the dependencies.
- Building info popup before committing to a build, with per-building cost
  and description.
- Ship crafter redrawn as a space factory with an assembly animation;
  mothership redrawn as a radial flagship; command centre as a plotting hub.
- Keyboard and mouse support (WASD, Q/E pivot, wheel zoom) for the web build.
- UI and font scaled up for phone use, via a custom Theme resource -
  gui/theme/default_font_size does not reach the default theme.
- Asteroids no longer spawn on top of the fleet's start position.
- Fleet formation origin derived from the layout's own offsets rather than
  the centroid, fixing the lurch when a lopsided formation started moving.
- Fleet.stop() brakes from the ship's TRUE motion (velocity +
  fleet_velocity). Ship zeroes its velocity when seated in its slot even
  while the anchor drags that slot forward, so braking from velocity alone
  stopped the fleet dead instead of coasting - and whether it did depended
  on the frame rate.

Animation architecture (issue #10)
- Buildings, projectiles and explosion VFX no longer animate by redrawing.
  Static geometry is rasterised once in _draw(); moving parts are NeonPiece
  children animated through node properties, which reuse the cached
  geometry. Every NeonDraw call expands into four antialiased polylines, so
  redrawing to move something re-tessellated all of it.

Test suite (issue #8): 1075s -> ~55s
- Runs from a copy on Termux's own filesystem. The project lives on
  Android's FUSE bridge, read through proot, where load("res://Main.tscn")
  alone cost 8.5s per test against ~2s natively - and nearly every test
  loads it.
- Runs 6 tests at a time, in a single proot-distro login, with output
  buffered per test and printed only on failure.
- --fixed-fps 60 pins delta instead of measuring the wall clock, so a test's
  result no longer depends on how busy the machine is. Without it,
  parallelism made two tests fail on 2 of 3 runs.
- A test passes only if it both exits 0 and prints ": PASS".
- 38 tests, green on three consecutive runs.

Bundles Carrois Gothic SC (Apache 2.0) with its licence text.

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

IconButton.gd

@@ -227,18 +227,31 @@ func _draw_crafter_icon(center: Vector2, pulse: float, s: float) -> void:
 
 
 func _draw_command_icon(center: Vector2, pulse: float, s: float) -> void:
-	# Diamond with three formation pips - "arrangement".
-	var d: float = 14.0 * s
+	# Hex plotting rim with spokes to a diamond hub, echoing the placed
+	# structure's silhouette: half the ports carry a formation token.
+	var hex_r: float = 11.0 * s
+	var hub_r: float = 4.0 * s
+	var hex: PackedVector2Array = PackedVector2Array()
+	for i in range(6):
+		var a: float = (float(i) / 6.0) * TAU + PI / 6.0
+		hex.append(center + Vector2(cos(a), sin(a)) * hex_r)
+	NeonDraw.draw_glowing_polygon(self, hex, _active_color(), pulse, core_color)
+
+	for i in range(6):
+		var a: float = (float(i) / 6.0) * TAU + PI / 6.0
+		var dir: Vector2 = Vector2(cos(a), sin(a))
+		NeonDraw.draw_glowing_line(self, center + dir * hub_r, center + dir * hex_r, _active_color(), pulse, 0.32 * s, core_color)
+		if i % 2 == 0:
+			var tip: Vector2 = center + dir * hex_r
+			var t: float = 2.6 * s
+			NeonDraw.draw_glowing_polygon(self, PackedVector2Array([
+				tip + Vector2(0, -t), tip + Vector2(t, 0), tip + Vector2(0, t), tip + Vector2(-t, 0),
+			]), _active_color(), pulse, core_color)
+
 	NeonDraw.draw_glowing_polygon(self, PackedVector2Array([
-		center + Vector2(0, -d), center + Vector2(d, 0),
-		center + Vector2(0, d), center + Vector2(-d, 0),
+		center + Vector2(0, -hub_r), center + Vector2(hub_r, 0),
+		center + Vector2(0, hub_r), center + Vector2(-hub_r, 0),
 	]), _active_color(), pulse, core_color)
-	for p in [Vector2(0, -5), Vector2(-5, 4), Vector2(5, 4)]:
-		NeonDraw.draw_glowing_polygon(self, PackedVector2Array([
-			center + (p + Vector2(0, -3)) * s,
-			center + (p + Vector2(-2.6, 2.4)) * s,
-			center + (p + Vector2(2.6, 2.4)) * s,
-		]), _active_color(), pulse, core_color)
 
 
 func _draw_extractor_icon(center: Vector2, pulse: float, s: float) -> void: