feat(stdlib): 2D Vector type + Vector.* namespace (issue #25)

Implement the Vec.* half of #25 under the proper (de-abbreviated) name
Vector, unblocking it with a self-contained value type instead of waiting
on the full #1 type system.

A Vector is two Q16.16 fixed components (x, y) packed into one i64 — a true
by-value type that lives in a register and never allocates (reuses the new
`long`/i64 support; llty maps `Vector` to i64). Fifteen operations, all
deterministic fixed-point reusing fx_mul/fx_div/fx_lerp and the @fn_fx_*
prelude: make/zero/x/y, add/sub/scale/dot, length/distance/normalize/lerp,
rotate/angle/from_angle.

New selfhost/emit_vector.ludic (wired into emit_ns_call + the frag list),
the `Vector` primitive type in llty and the grammars/LSP/JetBrains tokens,
docs (type-vector + 15 Vector.* pages + section), and a registered test.
Reseeded; C-free fixpoint holds; all suites green (45/25/29); site + check.py OK.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tools/ludic-tools/lsp.ludic

@@ -204,7 +204,7 @@ program LudicLsp {
     return c == 43 or c == 45 or c == 42 or c == 47 or c == 37 or c == 60 or c == 62 or c == 61 or c == 40 or c == 41 or c == 123 or c == 125 or c == 91 or c == 93 or c == 44 or c == 58 or c == 46 or c == 33 or c == 64 or c == 59
   }
   function is_type_word(w: pointer) -> bool {
-    return (w == "int") or (w == "long") or (w == "fixed") or (w == "bool") or (w == "entity") or (w == "string") or (w == "pointer") or (w == "byte") or (w == "words") or (w == "fixeds") or (w == "pointers") or (w == "void")
+    return (w == "int") or (w == "long") or (w == "fixed") or (w == "bool") or (w == "entity") or (w == "string") or (w == "pointer") or (w == "byte") or (w == "words") or (w == "fixeds") or (w == "pointers") or (w == "Vector") or (w == "void")
   }
   function is_phase_word(w: pointer) -> bool {
     return (w == "Start") or (w == "Input") or (w == "FixedUpdate") or (w == "Update") or (w == "LateUpdate") or (w == "Render")
@@ -1301,6 +1301,23 @@ program LudicLsp {
       if (meth == "fnv1a_64")  { return "Hash.fnv1a_64(s) -> long" }
       if (meth == "mix64")     { return "Hash.mix64(x) -> long" }
     }
+    if (ns == "Vector") {
+      if (meth == "make")       { return "Vector.make(x, y) -> Vector" }
+      if (meth == "zero")       { return "Vector.zero() -> Vector" }
+      if (meth == "x")          { return "Vector.x(v) -> fixed" }
+      if (meth == "y")          { return "Vector.y(v) -> fixed" }
+      if (meth == "add")        { return "Vector.add(a, b) -> Vector" }
+      if (meth == "sub")        { return "Vector.sub(a, b) -> Vector" }
+      if (meth == "scale")      { return "Vector.scale(v, s) -> Vector" }
+      if (meth == "dot")        { return "Vector.dot(a, b) -> fixed" }
+      if (meth == "length")     { return "Vector.length(v) -> fixed" }
+      if (meth == "distance")   { return "Vector.distance(a, b) -> fixed" }
+      if (meth == "normalize")  { return "Vector.normalize(v) -> Vector" }
+      if (meth == "lerp")       { return "Vector.lerp(a, b, t) -> Vector" }
+      if (meth == "rotate")     { return "Vector.rotate(v, angle) -> Vector" }
+      if (meth == "angle")      { return "Vector.angle(v) -> fixed" }
+      if (meth == "from_angle") { return "Vector.from_angle(a) -> Vector" }
+    }
     if (ns == "List") {
       if (meth == "len")      { return "List.len(s) -> int" }
       if (meth == "push")     { return "List.push(s, v)" }
@@ -2287,7 +2304,7 @@ program LudicLsp {
   }
   function comp_types(o: Buf) -> void {
     comp_item(o, "int", 14, "built-in type");  comp_item(o, "long", 14, "built-in type");  comp_item(o, "fixed", 14, "built-in type");  comp_item(o, "bool", 14, "built-in type")
-    comp_item(o, "entity", 14, "built-in type");  comp_item(o, "string", 14, "built-in type");  comp_item(o, "pointer", 14, "built-in type");  comp_item(o, "void", 14, "built-in type")
+    comp_item(o, "entity", 14, "built-in type");  comp_item(o, "string", 14, "built-in type");  comp_item(o, "pointer", 14, "built-in type");  comp_item(o, "Vector", 14, "built-in type");  comp_item(o, "void", 14, "built-in type")
   }
   function comp_builtins(o: Buf) -> void { var i = 0;  while i < len(g_builtins) { comp_item(o, g_builtins[i], 3, g_bsigs[i]);  i = i + 1 } }
   function on_completion(msg: JVal, id: JVal) -> void {

tools/ludic-tools/ludic_syntax.h

@@ -71,7 +71,7 @@ static const char* LUDIC_KW_STMT[] = {
     "and","or","not","break","continue","new","emit","cancel", 0
 };
 static const char* LUDIC_TYPES[] = {
-    "int","long","fixed","bool","entity","string","pointer","byte","words","fixeds","pointers","void", 0
+    "int","long","fixed","bool","entity","string","pointer","byte","words","fixeds","pointers","Vector","void", 0
 };
 static const char* LUDIC_PHASES[] = {
     "Start","Input","FixedUpdate","Update","LateUpdate","Render", 0