fix(mcp): rvlite tools now use ESM dynamic import for v0.2.x compatibility

[luminexo]

Summary

Fixes #302

The MCP server tools rvlite_sql, rvlite_cypher, and rvlite_sparql were failing with "rvlite package not installed" because they used CJS require('rvlite') on an ESM-only package (v0.2.x).

Root Cause

• rvlite v0.2.x removed CJS entry point
• require('rvlite') returns empty object {}
• MCP tools checked for rvlite.CypherEngine, found undefined, and reported "not installed"

Fix

• Changed from CJS require() to ESM dynamic import('rvlite/wasm')
• Added proper WASM initialization via initSync() with buffer
• Added engine caching to avoid re-initializing on every call
• Added helpful error messages for ESM-related failures

Testing

The fix follows the same pattern used in the issue report's workaround:

// Before (broken)
const rvlite = require('rvlite');  // → {} (empty object)
const db = new rvlite.Database();  // → TypeError

// After (fixed)
const rvlite = await import('rvlite/wasm');
const { readFileSync } = await import('fs');
rvlite.initSync(readFileSync('node_modules/rvlite/dist/wasm/rvlite_bg.wasm'));
const db = new rvlite.Database();  // → Works!

Files Changed

• npm/packages/ruvector/bin/mcp-server.js — Updated rvlite_sql, rvlite_cypher, rvlite_sparql handlers

Impact

• All rvlite_* MCP tools will now work correctly with rvlite v0.2.x
• Backward compatible with future versions that may restore CJS support
• No changes to external API — tools return same JSON format