build(core): leave the fuzz twin out of the published package

tests/fuzz_twin.rs includes ../../fuzz/src/lib.rs, which the tines-core
package doesn't ship, so the published source carried a test that can't
build (S13, packaging). `cargo package --list` now omits it and the
packaged crate verifies; tests/vectors.rs still ships, since src/lib.rs
includes it.

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

tines-core/Cargo.toml

@@ -15,6 +15,9 @@ categories = ["no-std", "embedded", "network-programming", "science::robotics"]
 # the wire format against the crate-private `Frame`, so `src/lib.rs` compiles
 # it into the unit tests instead (`#[path = "../tests/vectors.rs"]`).
 autotests = false
+# The fuzz twin includes `../../fuzz/src/lib.rs`, which isn't in this package,
+# so the published source would carry a test that can't build.
+exclude = ["tests/fuzz_twin.rs"]
 
 [features]
 default = ["alloc"]