terraphim-clients v1.21.5

Patch release for signed terraphim-agent and terraphim-grep updater assets.\n\nChanges:\n- Routes terraphim-agent update checks and updates to terraphim/terraphim-clients release assets.\n- Keeps terraphim-grep update support on terraphim/terraphim-clients.\n- Applies clippy/rustfmt cleanup in the touched terraphim-agent memory lifecycle section.\n- Attaches signed macOS ARM64 archives for terraphim-agent and terraphim-grep.\n\nAsset SHA-256:\n- terraphim-agent-1.21.5-aarch64-apple-darwin.tar.gz: fa5efaa208d2079ccb6027a1d6a2a72c8e87caa0e46e332f8a354e88437472b2\n- terraphim-grep-1.21.5-aarch64-apple-darwin.tar.gz: 886651fbc1cec5ae6f2a5c0fec9b1d72220b63bdd1a1861ff93e22e73963c271