feat: add ERANGE error handling for oversized number literals in lexer and Num.fromString

Replace TODO stubs with actual errno checks in readHexNumber, readNumber, and num_fromString to emit a "Number literal is too large." error when strtol/strtod overflow. Add three test files (literal_too_large.wren, hex_too_large.wren, from_string_too_large.wren) verifying compile-time and runtime error behavior for out-of-range numeric inputs.

test/number/from_string_too_large.wren

@@ -0,0 +1,2 @@
+var x = "999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999"
+var y = Num.fromString(x) // expect runtime error: Number literal is too large.

test/number/hex_too_large.wren

@@ -0,0 +1 @@
+var x = 0x999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999 // expect error: Error: Number literal was too large.

test/number/literal_too_large.wren

@@ -0,0 +1 @@
+var x = 999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999 // expect error: Error: Number literal was too large.