Per mara's review on PR #561: the previous commit kept
`./hive-ag3nt/prompts` in `cleanSrc` because
`hive-ag3nt::prompt::tests` had a compile-time
`include_str!("../prompts/system.md")`. That meant a prompt edit
still busted the cargo cache.
This change:
- Replaces the test-side `include_str!` with a runtime read from
`$HIVE_ASSETS_DIR/prompts/system.md` (with a CARGO_MANIFEST_DIR
fallback for plain `cargo test` from a checked-out repo).
- Drops `./hive-ag3nt/prompts` from `cleanSrc` — it's now
`craneLib.cleanCargoSource ./.` (Cargo.* + *.rs only).
- Sets `doCheck = false` on `packages.default` and lifts
`cargo test` into a separate `checks.cargo-test` derivation
that carries the `hyperhive-assets` build input. That scopes the
asset rebuild blast radius to the test check — `nix flake check`
still exercises the suite, but the binary derivation no longer
carries the assets dep.
Verified cache-invariance matrix (via `echo '' >> <f>; nix eval
.#default.outPath`):
| edit | default | cargo-test | clippy |
|-------------------------|---------|------------|--------|
| README.md | stable | stable | stable |
| branding/hyperhive.svg | stable | CHANGED | stable |
| nix/modules/* | stable | stable | stable |
| prompts/system.md | stable | CHANGED | stable |
| hive-c0re/src/main.rs | CHANGED | CHANGED | CHANGED |
(`cargo-test` CHANGED on prompts/branding is correct — tests
read the production template + need the assets output.)