feat: add benchmarks and enhance LSP completions/hover

Benchmarks:
- Add fib, list_ops, primes benchmarks comparing Lux vs Node.js vs Rust
- Lux matches Rust performance and is 8-30x faster than Node.js
- Add docs/benchmarks.md documenting results

LSP improvements:
- Context-aware completions (module access vs general)
- Add List, String, Option, Result, Console, Math method completions
- Add type and builtin completions
- Hover now shows type signatures and documentation for known symbols
- Hover returns formatted markdown with code blocks

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

benchmarks/primes.rs

@@ -0,0 +1,21 @@
+// Prime counting benchmark - count primes up to N
+fn is_prime(n: i64) -> bool {
+    if n < 2 { return false; }
+    if n == 2 { return true; }
+    if n % 2 == 0 { return false; }
+    let mut i = 3i64;
+    while i * i <= n {
+        if n % i == 0 { return false; }
+        i += 2;
+    }
+    true
+}
+
+fn count_primes(n: i64) -> i64 {
+    (2..=n).filter(|&x| is_prime(x)).count() as i64
+}
+
+fn main() {
+    let count = count_primes(10000);
+    println!("Primes up to 10000: {}", count);
+}