fix(client): clear the test debt — 2 production bugs, suite fully green (T-973 et al.)

Production fixes surfaced by honest test triage:
- hud_groups.gd: _set_group_z crashed on freed HUD nodes — the typed loop
  variable errors before the is_instance_valid guard runs; prune first
- fog_state.gd: _resize cleared _prev_visible (world-space keys survive
  resizes), so pre-resize tiles never decayed VISIBLE→EXPLORED (D-059)

Test debt (T-928/929/934/935/936/937/938/939, T-864, T-973): lambda
local-capture bugs rewritten with array captures (now assert exact
emission counts), e2e suites updated to the current handshake +
StartupMessage protocol and stream-aware reads against the live binary,
fog perf test measures steady state, chime test pins the shipped 800ms
catalog asset (D-067 amended separately), monologue gdUnit4 API typo,
battery-warning tests follow the MetaScreen on_open lifecycle. 3 sprint2
proof tests revived (corner_reveal had passed from the wrong tile — NPC3
blocks (18,14); route corrected). Soft-skips converted to real do_skip
reporting. T-1068: 7 orphan .gd.uid deleted, _format_pop/_format_radius
deduped into atlas_format.gd (preload, no class_name — headless cache).

Suite: 1264 cases/20 failures → 1268/0, independently re-verified
(2536/2536, exit 0).

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

client/tests/test_e2e_connection.gd

@@ -52,13 +52,41 @@ func after_test() -> void:
 		_server_pid = -1
 
 
+## Protocol handshake (#555, #175): the server sends a HandshakeMessage as the
+## first framed message; the client validates it and replies with a
+## StartupMessage carrying world_seed before any input is accepted.
+## Mirrors sim_bridge.gd's HANDSHAKING state.
+func _do_handshake(world_seed: int = 42) -> bool:
+	var msg := PackedByteArray()
+	var elapsed := 0.0
+	while elapsed < CONNECT_TIMEOUT:
+		_bridge.poll()
+		msg = _bridge.poll_message()
+		if msg.size() > 0:
+			break
+		await get_tree().create_timer(0.05).timeout
+		elapsed += 0.05
+	if msg.is_empty():
+		push_warning("No HandshakeMessage received within %.1fs" % CONNECT_TIMEOUT)
+		return false
+	var MP = load("res://addons/messagepack/messagepack.gd")
+	var decoded: Variant = MP.decode(msg)
+	if decoded.status != null or not (decoded.value is Dictionary):
+		push_warning("Malformed HandshakeMessage")
+		return false
+	var startup_bytes := Protocol.encode_startup_message(world_seed)
+	if startup_bytes.is_empty():
+		return false
+	return _bridge.send_message(startup_bytes) == OK
+
+
 # -- E2E: full round-trip through server binary --------------------------------
 
-func test_send_input_receive_snapshot() -> void:
+func test_send_input_receive_snapshot(
+	_do_skip := not FileAccess.file_exists(_server_binary_path()),
+	_skip_reason := "server binary not built — run `cargo build` in server/"
+) -> void:
 	var server_path := _server_binary_path()
-	if not FileAccess.file_exists(server_path):
-		push_warning("E2E test skipped: server binary not found at %s" % server_path)
-		return
 
 	# Spawn server with port rotation (retries if port is in use)
 	var spawned := await _spawn_server(server_path)
@@ -83,6 +111,12 @@ func test_send_input_receive_snapshot() -> void:
 
 	assert_bool(connected).is_true()
 
+	# Handshake + startup exchange (#555, #175) — required before input is accepted
+	var handshake_ok := await _do_handshake()
+	assert_bool(handshake_ok).override_failure_message(
+		"protocol handshake + StartupMessage exchange must complete (#555, #175)"
+	).is_true()
+
 	# Send batch input: MoveNorth at tick 0 (matching game_loop.rs test)
 	var inputs: Array = [{"tick": 0, "action_name": "MoveNorth"}]
 	var encoded := Protocol.encode_player_inputs(inputs)