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/tool/fs/edit.rs

@@ -1,9 +1,3 @@
-#![allow(
-    clippy::cast_possible_truncation,
-    clippy::cast_sign_loss,
-    clippy::cast_precision_loss,
-    clippy::cast_possible_wrap
-)]
 //! Tool: `edit` — replace a substring in a file with a new string.
 use super::super::check_graduated_checks;
 use super::super::resolve_path;

crates/zesdex-backend/src/tool/fs/read.rs

@@ -1,9 +1,3 @@
-#![allow(
-    clippy::cast_possible_truncation,
-    clippy::cast_sign_loss,
-    clippy::cast_precision_loss,
-    clippy::cast_possible_wrap
-)]
 //! Tool: `read` — display file contents with line numbers.
 use super::super::resolve_path;
 use super::super::Tool;