chore: clean up post-merge compiler warnings

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

rust/crates/runtime/src/hooks.rs

@@ -476,15 +476,6 @@ impl HookRunner {
     }
 }
 
-struct HookInvocation<'a> {
-    event: HookEvent,
-    tool_name: &'a str,
-    tool_input: &'a str,
-    tool_output: Option<&'a str>,
-    is_error: bool,
-    payload: &'a str,
-}
-
 enum HookCommandOutcome {
     Allow { parsed: ParsedHookOutput },
     Deny { parsed: ParsedHookOutput },