refactor: consolidate #![allow(clippy::cast_*)] to crate roots

Add the cast-allow block to zesdex-entities/src/lib.rs and
zesdex-utils/src/lib.rs (which lacked it), then remove from
65 sub-files across all 8 crates. Build and all 223 tests
continue to pass.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/zesdex-backend/src/app/mode/effort.rs

@@ -1,9 +1,3 @@
-#![allow(
-    clippy::cast_possible_truncation,
-    clippy::cast_sign_loss,
-    clippy::cast_precision_loss,
-    clippy::cast_possible_wrap
-)]
 //! Effort mode: cycles the agent's reasoning effort level, which scales the
 //! LLM's temperature and `max_tokens` for subsequent turns.
 use crate::app::state::rest::AppStateRest;

crates/zesdex-backend/src/app/mode/rewind.rs

@@ -1,9 +1,3 @@
-#![allow(
-    clippy::cast_possible_truncation,
-    clippy::cast_sign_loss,
-    clippy::cast_precision_loss,
-    clippy::cast_possible_wrap
-)]
 //! Rewind mode: restores a file to a pre-edit snapshot stored in the
 //! session's `SQLite` blob store.
 use crate::app::state::rest::AppStateRest;