build: exclude heavy test audio fixtures from the published crate

The package had ballooned to 22.3 MiB compressed (vs 3.79 MiB for 0.7.1),
over crates.io's 10 MiB limit, because large runtime test fixtures
(test.flac ~11 MB, test.wav ~7.7 MB, C7b9.wav, vec.bin, etc.) were being
bundled. They are loaded at runtime by #[cfg(test)] code via File::open,
never include_bytes!, so excluding them does not affect the package's
verify build or any consumer. Package now weighs 2.4 MiB compressed.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014b36jZYPfvNrb1AKaguFUq

Author: twitchax

kord/Cargo.toml

@@ -10,7 +10,7 @@ homepage = "https://github.com/twitchax/kord"
 repository = "https://github.com/twitchax/kord"
 keywords = ["cli", "music", "theory", "jazz", "chords"]
 categories = ["command-line-utilities"]
-exclude = ["samples/**/*", "noise/**/*", "../kord-web/"]
+exclude = ["samples/**/*", "noise/**/*", "../kord-web/", "tests/*.wav", "tests/*.flac", "tests/*.mp3", "tests/*.mid", "tests/vec.bin"]
 
 [lib]
 name = "klib"