feat(align): SMF parser, role guess, reference manifest

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/align/roles.ts

@@ -0,0 +1,17 @@
+import type { Role } from "../core/types.ts";
+import type { RefTrack } from "./smf.ts";
+
+// Best-effort role for a reference MIDI track; null = unmapped (excluded from scoring until the user maps it).
+export function guessRole(t: RefTrack): Role | null {
+  if (t.isDrums) return "drums";
+  const n = t.name.trim().toLowerCase();
+  if (/vocal|voice|vox|sing/.test(n)) return "vocals";
+  if (/bass/.test(n)) return "bass";
+  if (/guitar|delay/.test(n)) return "guitar";
+  if (/piano|key|synth|organ/.test(n)) return "keys";
+  const p = t.program;
+  if (p >= 32 && p <= 39) return "bass";
+  if (p >= 24 && p <= 31) return "guitar";
+  if ((p >= 0 && p <= 7) || (p >= 16 && p <= 23) || (p >= 88 && p <= 95)) return "keys";
+  return null;
+}