feat: add Solidity language support

[guiltylotus]

Summary

• Adds .sol file indexing via a vendored tree-sitter-solidity WASM (v1.2.13)
• Extracts contracts and libraries as class, interfaces as interface, structs, enums, functions, modifiers, events, constructors, fallback/receive, state variables, constants, and imports — all with full signature capture
• Registers solidity in LANGUAGES, EXTENSION_MAP, WASM_GRAMMAR_FILES, the vendored WASM path check, and the display name map

What gets indexed

Solidity construct	Graph kind
contract_declaration, library_declaration	class
interface_declaration	interface
struct_declaration	struct
enum_declaration / enum_value	enum / enum_member
function_definition, modifier_definition, event_definition	method / function
constructor_definition, fallback_receive_definition	function (via visitNode)
state_variable_declaration	variable with type signature
constant_variable_declaration	constant
import_directive	import

Benchmark

Language	Cost	Tokens	Time	Tool calls
Solidity · ~343 files	8% cheaper	25% fewer	10% faster	29% fewer

Notes

• WASM vendored from tree-sitter-solidity@1.2.13 (same vendoring pattern as Lua, Luau, Pascal, Scala)
• constructor_definition and fallback_receive_definition have no name field in the AST — handled via the visitNode hook, naming them "constructor", "fallback", or "receive" respectively
• Solidity external visibility is mapped to public in the graph (it means callable from outside the contract)

🤖 Generated with Claude Code