Spill oversized PreToolUse additionalContext (#22529)

# Why

`PreToolUse.additionalContext` became model-visible after #20692, but
the hook-output spilling path from #21069 never picked up that newer
lane. As a result, oversized `PreToolUse` context could bypass the
truncation/spill treatment that already applies to the other hook
outputs Codex forwards to the model.

# What

- Run `PreToolUseOutcome.additional_contexts` through
`maybe_spill_texts(...)`
- Add an integration test proving a large `PreToolUse.additionalContext`
is replaced with a truncated preview plus spill-file pointer, while the
full text is preserved on disk.

codex-rs/hooks/src/engine/mod.rs

@@ -4,8 +4,6 @@ pub(crate) mod dispatcher;
 pub(crate) mod output_parser;
 pub(crate) mod schema_loader;
 
-use std::collections::HashMap;
-
 use crate::events::compact::PostCompactRequest;
 use crate::events::compact::PreCompactOutcome;
 use crate::events::compact::PreCompactRequest;
@@ -32,6 +30,7 @@ use codex_protocol::protocol::HookRunSummary;
 use codex_protocol::protocol::HookSource;
 use codex_protocol::protocol::HookTrustStatus;
 use codex_utils_absolute_path::AbsolutePathBuf;
+use std::collections::HashMap;
 
 #[derive(Debug, Clone)]
 pub(crate) struct CommandShell {
@@ -180,7 +179,13 @@ impl ClaudeHooksEngine {
     }
 
     pub(crate) async fn run_pre_tool_use(&self, request: PreToolUseRequest) -> PreToolUseOutcome {
-        crate::events::pre_tool_use::run(&self.handlers, &self.shell, request).await
+        let session_id = request.session_id;
+        let mut outcome =
+            crate::events::pre_tool_use::run(&self.handlers, &self.shell, request).await;
+        outcome.additional_contexts = self
+            .maybe_spill_texts(session_id, outcome.additional_contexts)
+            .await;
+        outcome
     }
 
     pub(crate) async fn run_permission_request(