add tree-sitter syntax highlighting via dart:ffi

Vendor libtree-sitter.so (v0.26.8, wasmtime 44.0 statically linked)
and call its C API through dart:ffi. Grammar WASM files are loaded by
tree-sitter's embedded wasmtime engine via ts_wasm_store_load_language.

48 grammars compiled with tree-sitter build --wasm, 48 highlight
queries (42 from upstream repos, 6 written in-house for comment,
erlang, gdscript, gitignore, hcl, hlsl, swift). SQLite grammar
replaces full SQL (974K-line parser exhausted RAM at compile time).

Removes wasm_run and wasm_run_flutter — they downloaded a 22 MB
binary from GitHub at first launch, violating the no-network-on-
default-launch-path policy.

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

app/assets/queries/cpp.scm

@@ -0,0 +1,77 @@
+; Functions
+
+(call_expression
+  function: (qualified_identifier
+    name: (identifier) @function))
+
+(template_function
+  name: (identifier) @function)
+
+(template_method
+  name: (field_identifier) @function)
+
+(template_function
+  name: (identifier) @function)
+
+(function_declarator
+  declarator: (qualified_identifier
+    name: (identifier) @function))
+
+(function_declarator
+  declarator: (field_identifier) @function)
+
+; Types
+
+((namespace_identifier) @type
+ (#match? @type "^[A-Z]"))
+
+(auto) @type
+
+; Constants
+
+(this) @variable.builtin
+(null "nullptr" @constant)
+
+; Modules
+(module_name
+  (identifier) @module)
+
+; Keywords
+
+[
+ "catch"
+ "class"
+ "co_await"
+ "co_return"
+ "co_yield"
+ "constexpr"
+ "constinit"
+ "consteval"
+ "delete"
+ "explicit"
+ "final"
+ "friend"
+ "mutable"
+ "namespace"
+ "noexcept"
+ "new"
+ "override"
+ "private"
+ "protected"
+ "public"
+ "template"
+ "throw"
+ "try"
+ "typename"
+ "using"
+ "concept"
+ "requires"
+ "virtual"
+ "import"
+ "export"
+ "module"
+] @keyword
+
+; Strings
+
+(raw_string_literal) @string