fix: stop lexing negative numbers as single tokens to fix parsing of subtraction

Previously, the lexer greedily consumed a `-` followed by a digit as a single negative number token, causing "1 -1" to be lexed as two number tokens instead of a minus operator and a positive literal. This broke parsing of subtraction expressions without spaces.

Now `-` always emits a TOKEN_MINUS, and the parser handles unary negation. This is a breaking change: `-16.sqrt` is now parsed as `-(16.sqrt)` instead of `(-16).sqrt`, requiring parentheses for negative method receivers. All number method tests (abs, ceil, floor, sqrt, toString) are updated to use explicit parentheses for negative receivers.

test/number/abs.wren

@@ -1,6 +1,6 @@
-IO.print(123.abs)    // expect: 123
-IO.print(-123.abs)   // expect: 123
-IO.print(0.abs)      // expect: 0
-IO.print(-0.abs)     // expect: 0
-IO.print(-0.12.abs)  // expect: 0.12
-IO.print(12.34.abs)  // expect: 12.34
+IO.print(123.abs)      // expect: 123
+IO.print((-123).abs)   // expect: 123
+IO.print(0.abs)        // expect: 0
+IO.print((-0).abs)     // expect: 0
+IO.print((-0.12).abs)  // expect: 0.12
+IO.print(12.34.abs)    // expect: 12.34

test/number/ceil.wren

@@ -1,8 +1,8 @@
-IO.print(123.ceil)    // expect: 123
-IO.print(-123.ceil)   // expect: -123
-IO.print(0.ceil)      // expect: 0
-IO.print(-0.ceil)     // expect: -0
-IO.print(0.123.ceil)  // expect: 1
-IO.print(12.3.ceil)   // expect: 13
-IO.print(-0.123.ceil) // expect: -0
-IO.print(-12.3.ceil)  // expect: -12
+IO.print(123.ceil)      // expect: 123
+IO.print((-123).ceil)   // expect: -123
+IO.print(0.ceil)        // expect: 0
+IO.print((-0).ceil)     // expect: -0
+IO.print(0.123.ceil)    // expect: 1
+IO.print(12.3.ceil)     // expect: 13
+IO.print((-0.123).ceil) // expect: -0
+IO.print((-12.3).ceil)  // expect: -12

test/number/floor.wren

@@ -1,8 +1,8 @@
-IO.print(123.floor)    // expect: 123
-IO.print(-123.floor)   // expect: -123
-IO.print(0.floor)      // expect: 0
-IO.print(-0.floor)     // expect: -0
-IO.print(0.123.floor)  // expect: 0
-IO.print(12.3.floor)   // expect: 12
-IO.print(-0.123.floor) // expect: -1
-IO.print(-12.3.floor)  // expect: -13
+IO.print(123.floor)      // expect: 123
+IO.print((-123).floor)   // expect: -123
+IO.print(0.floor)        // expect: 0
+IO.print((-0).floor)     // expect: -0
+IO.print(0.123.floor)    // expect: 0
+IO.print(12.3.floor)     // expect: 12
+IO.print((-0.123).floor) // expect: -1
+IO.print((-12.3).floor)  // expect: -13

test/number/sqrt.wren

@@ -1,10 +1,10 @@
 IO.print(4.sqrt)        // expect: 2
 IO.print(1000000.sqrt)  // expect: 1000
 IO.print(1.sqrt)        // expect: 1
-IO.print(-0.sqrt)       // expect: -0
+IO.print((-0).sqrt)     // expect: -0
 IO.print(0.sqrt)        // expect: 0
 IO.print(2.sqrt)        // expect: 1.4142135623731
 
-IO.print(-4.sqrt.isNan) // expect: true
+IO.print((-4).sqrt.isNan) // expect: true
 
 // TODO: Tests for sin and cos.

test/number/to_string.wren

@@ -1,5 +1,5 @@
 IO.print(123.toString == "123") // expect: true
-IO.print(-123.toString == "-123") // expect: true
-IO.print(-0.toString == "-0") // expect: true
+IO.print((-123).toString == "-123") // expect: true
+IO.print((-0).toString == "-0") // expect: true
 IO.print(12.34.toString == "12.34") // expect: true
-IO.print(-0.0001.toString == "-0.0001") // expect: true
+IO.print((-0.0001).toString == "-0.0001") // expect: true