feat(serve): add optimized llama-server launcher with n-gram speculation

Add `make serve` and `make serve-ngram` for launching llama-server with
baked-in optimal settings (Vulkan RADV, q4_0 KV cache, flash attention,
no-mmap, full GPU offload). N-gram speculative decoding gives 1.1-1.4x
tg speedup on repetitive content without upstream PR dependencies.
Update Phase 5 status: MTP is months away (4 unmerged PRs, no MoE
support), draft-model speculation stalled on ROCm buffer crashes.

bin/serve

@@ -0,0 +1,5 @@
+#!/usr/bin/env bash
+# Server dispatcher
+set -euo pipefail
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+exec bash "$SCRIPT_DIR/scripts/serve/launch.sh" "$@"