* fix(docs): replace dead ci-keys.zkmopro.org download links

ci-keys.zkmopro.org stopped resolving, so following the setup guide or the
EthTaipei workshop hit "curl: (6) Could not resolve host". Point at the
fixtures committed in this repo and in rust-rapidsnark instead, pinned to a
tag or commit so they cannot drift. The versioned 0.1 and 0.2 copies carried
the same dead host, so they are updated too.

keccak256.json becomes circuit-registry's keccak256/input.json, which is
byte-identical to the input the workshop already pastes inline.

Also note that rapidsnark has no x86_64-apple-ios prebuilt, since
rust-rapidsnark 0.1.4 dropped that target, and building it now needs
RAPIDSNARK_LIB_DIR.

Finally, cover the rapidsnark feature in cli_template_tests. Scaffolded
projects leave it off, so nothing in CI compiled rust-rapidsnark or fetched
its prebuilt libraries, which is why a download endpoint could break for
users without CI noticing. Runs on both macos-latest and ubuntu-latest.

Refs #724

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

* fix(ci): point rapidsnark guard error at circom.rs

The grep guard's error message named write_toml.rs, which only emits the
# CIRCOM_DEPENDENCIES marker. The circom-prover line the sed pattern
matches comes from the DEPENDENCIES const in cli/src/init/circom.rs.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix: remove unused ubrn WASM scaffolding

* correctly formatted rust code