ci(ruview-swarm): install clippy on the pinned 1.89 toolchain

The clippy job failed with "cargo-clippy is not installed for the
toolchain '1.89'". v2/rust-toolchain.toml pins channel "1.89" (profile
"minimal", no clippy); dtolnay@stable installed clippy on the floating
"stable" toolchain, but the override makes cargo use the separate "1.89"
toolchain in working-directory v2. Pin the toolchain input to "1.89" so
clippy lands on the toolchain cargo actually runs.

(The real clippy lint it then catches — manual_is_multiple_of — was fixed
in 29e698a05.)

Co-Authored-By: claude-flow <ruv@ruv.net>