fix(guard): remove unused org-ownership functions blocking release (#4290)

## Problem

The Release workflow ([run
#24740822133](https://github.com/github/gh-aw-mcpg/actions/runs/24740822133))
failed in the `docker` job because the Rust guard build has `-D
warnings` enabled and two functions trigger dead_code warnings:

```
error: function `get_cached_owner_is_org` is never used
  --> src/labels/backend.rs:63

error: function `is_repo_org_owned` is never used
  --> src/labels/backend.rs:282
```

## Fix

Remove the two unused functions (`get_cached_owner_is_org` and
`is_repo_org_owned`) and their associated tests. These were added for
future org-ownership detection but are never called from production
code.

The cache *setter* (`set_cached_owner_is_org`) is retained — it's called
during `is_repo_private` lookups to populate the owner-type cache for
when these functions are needed later.

## Removed
- `get_cached_owner_is_org()` — private cache reader (line 63)
- `is_repo_org_owned()` — public API (line 282)
- `test_is_repo_org_owned_uses_cache` — test
- `test_is_repo_org_owned_empty_args` — test

## Verification
`make agent-finished` passes (format, build, lint, all tests including
Rust guard).

Author: lpcox

guards/github-guard/rust-guard/src/labels/backend.rs

@@ -60,13 +60,6 @@ fn set_cached_repo_visibility(repo_id: &str, is_private: bool) {
     }
 }
 
-fn get_cached_owner_is_org(repo_id: &str) -> Option<bool> {
-    repo_owner_type_cache()
-        .lock()
-        .ok()
-        .and_then(|cache| cache.get(repo_id).copied())
-}
-
 fn set_cached_owner_is_org(repo_id: &str, is_org: bool) {
     if let Ok(mut cache) = repo_owner_type_cache().lock() {
         cache.insert(repo_id.to_string(), is_org);
@@ -271,21 +264,6 @@ pub fn is_repo_private_with_callback(
     get_cached_repo_visibility(&repo_id)
 }
 
-/// Check whether a repository is owned by an organization (vs a personal account).
-/// This is determined from the `owner.type` field in the search_repositories response,
-/// which is cached alongside repo visibility during `is_repo_private` calls.
-///
-/// Returns:
-/// - `Some(true)` if the owner is an Organization
-/// - `Some(false)` if the owner is a User (personal account)
-/// - `None` if the owner type could not be determined
-pub fn is_repo_org_owned(owner: &str, repo: &str) -> Option<bool> {
-    if owner.is_empty() || repo.is_empty() {
-        return None;
-    }
-    let repo_id = format!("{}/{}", owner, repo);
-    get_cached_owner_is_org(&repo_id)
-}
 
 /// Fetch pull request facts used for integrity derivation.
 pub fn get_pull_request_facts_with_callback(
@@ -1217,12 +1195,6 @@ mod tests {
 
     // --- Owner type (org vs user) tests ---
 
-    fn clear_owner_type_cache_for_tests() {
-        if let Ok(mut cache) = repo_owner_type_cache().lock() {
-            cache.clear();
-        }
-    }
-
     #[test]
     fn test_owner_type_from_repo_object_org() {
         let item = serde_json::json!({
@@ -1309,23 +1281,6 @@ mod tests {
         });
         assert_eq!(extract_owner_is_org(&response, "myorg/myrepo"), None);
     }
-
-    #[test]
-    fn test_is_repo_org_owned_uses_cache() {
-        clear_owner_type_cache_for_tests();
-        set_cached_owner_is_org("cached-org/repo", true);
-        assert_eq!(is_repo_org_owned("cached-org", "repo"), Some(true));
-
-        set_cached_owner_is_org("cached-user/repo", false);
-        assert_eq!(is_repo_org_owned("cached-user", "repo"), Some(false));
-        clear_owner_type_cache_for_tests();
-    }
-
-    #[test]
-    fn test_is_repo_org_owned_empty_args() {
-        assert_eq!(is_repo_org_owned("", "repo"), None);
-        assert_eq!(is_repo_org_owned("owner", ""), None);
-    }
 }
 
 fn repo_visibility_from_items(value: &Value, repo_id: &str) -> Option<bool> {