fix: exclude fuzz directory from workspace

The fuzz directory contains cargo-fuzz targets that require nightly Rust
and have incompatible build configurations with the main workspace
(ASAN, sanitizer coverage, custom RUSTFLAGS, etc.).

Previously, the fuzz directory was not explicitly excluded, causing
workspace resolution errors in CI:
  error: current package believes it's in a workspace when it's not

Added fuzz/ to workspace.exclude to keep it as an independent package,
similar to wraith-xdp and spectre-implant which also have special
build requirements.

Fixes Fuzz workflow failures in CI.

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

Author: doublegate

Cargo.toml

@@ -36,6 +36,7 @@ members = [
 exclude = [
     "crates/wraith-xdp",
     "clients/wraith-redops/spectre-implant",
+    "fuzz",
 ]
 
 [workspace.package]