v0.2: Pico-8 Lua dialect grammar and language

Reorganize into grammars/<name>/ subdirs ( Zed's [grammars.*] supports
a `path` field, so both grammars ship from this repo without a sibling-
repo split ). Vendor tree-sitter-lua as the fork base for tree-sitter-
pico8-lua; upstream MIT license preserved at grammars/pico-8-lua/
UPSTREAM-LICENSE.md.

Dialect features added: != as ~= alias, \ integer divide, ^^ binary xor,
>>> / <<> / >>< shifts and rotates, compound-assignment statements,
memory peek prefixes @ % $ (% coexists with binary modulo), single-line
`if (cond) stmt [else stmt]` and `while (cond) stmt`, statement-level
print shorthand ?, and `#include path` directives. Identifier rule no
longer accepts ! ? @ $ ( upstream did ).

Pico-8 Lua language ( languages/pico-8-lua/, suffix .p8lua ) ships
highlights with the full ~110 PICO-8 builtins as @function.builtin.
The cart injection now hands __lua__ bodies to pico-8-lua, so .p8 carts
and bare .p8lua files share the dialect-aware grammar. Examples updated
to exercise the dialect end-to-end.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

examples/hello.p8

@@ -1,14 +1,24 @@
 pico-8 cartridge // http://www.pico-8.com
 version 42
 __lua__
--- hello cartridge
+-- hello cartridge — exercises Pico-8 dialect features
+#include shared.p8lua
+
 function _init()
  cls()
+ t = 0
+end
+
+function _update()
+ t += 1
+ if (btn(4)) sweep_palette()
+ move()
 end
 
 function _draw()
  cls(1)
- print("hello pico-8", 30, 60, 7)
+ draw_blob()
+ ?"frame:"..t, 0, 120, 7
 end
 __gfx__
 00000000111111110000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000

examples/shared.p8lua

@@ -0,0 +1,30 @@
+-- shared.p8lua: included into hello.p8 via #include
+-- demonstrates Pico-8 dialect features outside a __lua__ section.
+
+local x, y = 64, 64
+
+function move()
+ if (btn(0)) x-=1
+ if (btn(1)) x+=1
+ if (btn(2)) y-=1
+ if (btn(3)) y+=1
+ x = mid(0, x, 127)
+ y = mid(0, y, 127)
+end
+
+function draw_blob()
+ cls(1)
+ circfill(x, y, 5, 7)
+ ?"x="..x..",y="..y, 0, 0, 7
+end
+
+-- peek/poke via prefix shorthands
+function sweep_palette()
+ for i=0,15 do
+  poke(0x5f10+i, %0x5f10 ^^ i)
+ end
+end
+
+-- single-line while with compound assignment body
+local i = 0
+while (i < 8) i += 1