Initial commit: Transcience MVP

Top-down twin-stick bullet-hell, Godot 4.7, server-authoritative dedicated
server with client-side prediction. Clients send input only; the server
resolves every hit for both players and enemies (no PvP).

- SimWorld: whole simulation as plain RefCounted objects (no nodes, no
  physics server), ~0.24ms/tick at peak load -- runs headless for free and
  drives 78 tests in under a second
- BulletPool: struct-of-arrays bullet storage, replicated as spawn/despawn
  events rather than per-tick state
- Emitter framework (Ring/AimedSpread/WallGap/ArcSweep) shared by trash
  enemies and bosses -- a new boss is data in src/content/content.gd, no
  simulation changes
- The Warden of the Fold: stationary 4-phase boss built entirely on that
  format
- Lobby hub with a portal into on-demand dungeon instances; one process
  hosts the hub plus every concurrent dungeon
- Emergency escape: 3s server-owned channel, cancelled by damage
- tools/check.sh, test.sh (GUT), smoke.sh (real server + bot clients over
  ENet), bench.gd; git hooks wired to the same scripts
- docs/ARCHITECTURE.md, NETCODE.md, WORKFLOW.md, ROADMAP.md

tests/unit/test_input_frame.gd

@@ -0,0 +1,43 @@
+extends GutTest
+## The input packet is the only thing a client can put on the wire, so its
+## bounds are a security surface as much as a format.
+
+
+func _round_trip(f: InputFrame) -> InputFrame:
+	var b := StreamPeerBuffer.new()
+	b.big_endian = false
+	f.write(b)
+	b.seek(0)
+	return InputFrame.read(b)
+
+
+func test_round_trip_preserves_tick_and_buttons() -> void:
+	var f := InputFrame.make(123456, Vector2(0.5, -0.25), 1.75,
+		InputFrame.BTN_FIRE | InputFrame.BTN_ESCAPE)
+	var out := _round_trip(f)
+	assert_eq(out.tick, 123456)
+	assert_true(out.pressed(InputFrame.BTN_FIRE))
+	assert_true(out.pressed(InputFrame.BTN_ESCAPE))
+	assert_false(out.pressed(InputFrame.BTN_INTERACT))
+
+
+func test_move_survives_quantisation_within_tolerance() -> void:
+	var out := _round_trip(InputFrame.make(1, Vector2(0.5, -0.25), 0.0, 0))
+	assert_almost_eq(out.move.x, 0.5, 0.01)
+	assert_almost_eq(out.move.y, -0.25, 0.01)
+
+
+func test_aim_survives_quantisation() -> void:
+	var out := _round_trip(InputFrame.make(1, Vector2.ZERO, 2.5, 0))
+	assert_almost_eq(out.aim, 2.5, 0.001)
+
+
+func test_oversized_move_cannot_be_expressed_on_the_wire() -> void:
+	var out := _round_trip(InputFrame.make(1, Vector2(50.0, 50.0), 0.0, 0))
+	assert_lt(out.move.length(), 1.45, "the byte encoding must cap the move vector")
+
+
+func test_frame_is_exactly_the_declared_size() -> void:
+	var b := StreamPeerBuffer.new()
+	InputFrame.make(1, Vector2.ONE, 1.0, 7).write(b)
+	assert_eq(b.data_array.size(), InputFrame.SIZE)