Phase 7: netfox + godot-jolt stack upgrade

Stack installed:
- netfox v1.35.3 (core + extras + noray + internals)
- godot-jolt v0.16.0-stable

Architecture:
- Server: ENet transport (works headless, no netfox deps)
- Client/Editor: netfox rollback (RollbackSynchronizer, TickInterpolator)

New/modified:
- docs/migration-netfox-plan.md — migration architecture
- scripts/network/network_manager.gd — netfox-aware ENet fallback
- scripts/network/player.gd — clean base player
- client/characters/player_netfox.gd — rollback player w/ WeaponManager
- client/characters/input/player_net_input.gd — BaseNetInput subclass
- client/characters/character/fps_character_controller.gd — netfox input feed
- client/weapons/ — weapon data, registry, TacticalWeaponHitscan, WeaponManager
- client/scripts/round_replicator.gd — client-side round state bridge
- server/scripts/round_manager.gd — improved state machine
- server/scripts/plugin_api/plugin_manager.gd — refined plugin system
- config: enemy_tag, ally_tag for meatball targeting

Removed: old C++ SimulationServer GDExtension (replaced by netfox rollback)

tests/test_utils.gd

@@ -0,0 +1,111 @@
+extends Node
+class_name TestUtils
+
+# ═══════════════════════════════════════════════════════════════════════════
+#  TestUtils — Minimal assertion framework for headless Godot unit tests
+#
+#  Usage:
+#    var tu = TestUtils.new()
+#    add_child(tu)
+#    tu.describe("Movement validation")
+#    tu.assert_eq(result.x, 5, "x should be 5")
+#    tu.assert_true(valid, "should be valid")
+#    tu.finish()  # prints summary
+# ═══════════════════════════════════════════════════════════════════════════
+
+var _passed: int = 0
+var _failed: int = 0
+var _current_suite: String = ""
+var _assertions_in_suite: int = 0
+
+func describe(name: String) -> void:
+	"""Start a named test suite/section."""
+	_current_suite = name
+	_assertions_in_suite = 0
+	print("\n  === " + name + " ===")
+
+func assert_eq(got, expected, msg: String = "") -> void:
+	_assertions_in_suite += 1
+	if got == expected:
+		_passed += 1
+	else:
+		_failed += 1
+		var detail = "got '%s', expected '%s'" % [str(got), str(expected)]
+		print("    [FAIL] " + msg + " — " + detail)
+
+func assert_ne(got, unexpected, msg: String = "") -> void:
+	_assertions_in_suite += 1
+	if got != unexpected:
+		_passed += 1
+	else:
+		_failed += 1
+		print("    [FAIL] " + msg + " — got '%s' which matches unexpected value" % str(got))
+
+func assert_true(cond: bool, msg: String = "") -> void:
+	_assertions_in_suite += 1
+	if cond:
+		_passed += 1
+	else:
+		_failed += 1
+		print("    [FAIL] " + msg + " — expected true, got false")
+
+func assert_false(cond: bool, msg: String = "") -> void:
+	_assertions_in_suite += 1
+	if not cond:
+		_passed += 1
+	else:
+		_failed += 1
+		print("    [FAIL] " + msg + " — expected false, got true")
+
+func assert_almost_eq(got: float, expected: float, tolerance: float = 0.001, msg: String = "") -> void:
+	_assertions_in_suite += 1
+	if abs(got - expected) <= tolerance:
+		_passed += 1
+	else:
+		_failed += 1
+		var detail = "got %.4f, expected %.4f ± %.4f" % [got, expected, tolerance]
+		print("    [FAIL] " + msg + " — " + detail)
+
+func assert_violation(result: Dictionary, category: int, msg: String = "") -> void:
+	"""Assert the validation result contains at least one violation of the given category."""
+	_assertions_in_suite += 1
+	for v in result.get("violations", []):
+		if v.get("category", -1) == category:
+			_passed += 1
+			return
+	_failed += 1
+	print("    [FAIL] " + msg + " — expected violation category " + str(category) + ", none found")
+
+func assert_no_violation(result: Dictionary, msg: String = "") -> void:
+	"""Assert the validation result has zero violations."""
+	_assertions_in_suite += 1
+	var count = result.get("violations", []).size()
+	if count == 0:
+		_passed += 1
+	else:
+		_failed += 1
+		print("    [FAIL] " + msg + " — expected 0 violations, got " + str(count) + ": " + str(result["violations"]))
+
+func assert_corrected(result: Dictionary, field: String, msg: String = "") -> void:
+	"""Assert the result's corrected dict has a different value for `field` than the original."""
+	_assertions_in_suite += 1
+	if result.get("corrected", {}).has(field):
+		_passed += 1
+	else:
+		_failed += 1
+		print("    [FAIL] " + msg + " — expected correction in field '%s', none found" % field)
+
+func finish() -> void:
+	"""Print test summary and return exit code via OS."""
+	var total = _passed + _failed
+	print("\n  ──────────────────────────────────────")
+	print("  Suite: " + _current_suite)
+	print("  Passed: %d / %d" % [_passed, total])
+	if _failed > 0:
+		print("  FAILED: %d test(s)" % _failed)
+	else:
+		print("  All passed.")
+	print("")
+
+func exit_code() -> int:
+	return 0 if _failed == 0 else 1