feat: Add ArkTS language support (.ets)

[FurryWolfX]

Problem

CodeGraph currently does not support parsing .ets (ArkTS) files. ArkTS is the primary language for OpenHarmony/HarmonyOS application development.

Context

A mature tree-sitter-arkts parser is already available in the community.

Request

Add ArkTS (*.ets) language support to CodeGraph.

Proposed Solution

Integrate the tree-sitter-arkts parser into CodeGraph:

1. Register .ets file extension mapping to tree-sitter-arkts grammar in CodeGraph
2. Map ArkTS AST node types (function, class, interface, method, variable, import, etc.) to CodeGraph's generic node model
3. Verify indexing capabilities: symbol search, call chain, impact analysis

Related

• tree-sitter-arkts: https://github.com/Million-mo/tree-sitter-arkts