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>

grammars/p8-cart/tree-sitter.json

@@ -0,0 +1,29 @@
+{
+  "grammars": [
+    {
+      "name": "p8-cart",
+      "camelcase": "P8Cart",
+      "scope": "source.p8-cart",
+      "path": ".",
+      "file-types": [
+        "p8"
+      ]
+    }
+  ],
+  "metadata": {
+    "version": "0.0.1",
+    "license": "0BSD",
+    "description": "tree-sitter grammar for the PICO-8 .p8 cartridge text format",
+    "links": {
+      "repository": "https://github.com/tree-sitter/tree-sitter-p8-cart"
+    }
+  },
+  "bindings": {
+    "c": true,
+    "go": true,
+    "node": true,
+    "python": true,
+    "rust": true,
+    "swift": true
+  }
+}