aprender-serve published tarball: tokenizer_tests_unk_3609 include_bytes! tests/fixtures, which Cargo.toml excludes (/tests/) #4193

Part of #4175. Found in aprender-3a's clean-room run on v0.69.1 (d8a6df5).

Test-only. The published lib is fine: the failing kind is lib test.

crates/aprender-serve/src/tokenizer_tests_unk_3609.rs (#3609, a #[cfg(test)] module) does include_bytes!("../tests/fixtures/gguf-header-slices/{qwen3.5-0.8b,tinyllama-1.1b-chat}.gguf-header"). crates/aprender-serve/Cargo.toml has exclude = [ …, "/tests/", … ], so cargo package drops the fixtures and the lib test cannot compile out of tree:

src/tokenizer_tests_unk_3609.rs:18:5: error: couldn't read `pkgs/aprender-serve-0.69.1/src/../tests/fixtures/gguf-header-slices/qwen3.5-0.8b.gguf-header`
src/tokenizer_tests_unk_3609.rs:20:5: error: couldn't read `pkgs/aprender-serve-0.69.1/src/../tests/fixtures/gguf-header-slices/tinyllama-1.1b-chat.gguf-header`

This is not #4048: that ticket is the contracts/kernel-fusion-v1.yaml include in fusion_call_site_guard_3985.rs, the third error in the same target.

Fix (pick one, in the #4175 review): (a) move the two header slices plus MANIFEST/generate.py under src/fixtures/gguf-header-slices/, the pattern src/fixtures/chat_template_3990/ already uses; the slices are small and ship with the crate. Or (b) the #4183 helper with a skip out of tree. (a) keeps the test running for crates.io users; check the slice sizes against the crate size budget first.

done_when: cargo build -p aprender-serve --lib --tests from the unpacked tarball has no error at tokenizer_tests_unk_3609.rs, and the #3609 rows still pass in tree.