Organize bundled Rust resources under asset directories (#41477)

## Why

The `core` and `tui` Bazel targets treated nearly their entire crate trees as
compile-time data, mixing embedded runtime resources with source files and test
fixtures.

## What changed

- Move embedded resources for `core` and `tui` into dedicated `assets/`
  directories and update their `include_str!` paths.
- Restrict Bazel compile data to explicit asset and frame directories.
- Move test-only prompts into `tests/fixtures`, resolve the core prompt through
  `find_resource!`, and reuse the integration-test file glob when assembling
  Bazel test data.

GitOrigin-RevId: eee9b0e41df77ea2604215a7f7333a6fe8317bfa

codex-rs/core/tests/suite/guardian_review.rs

@@ -753,7 +753,7 @@ async fn guardian_node_repl_policy_follows_production_approval_path(
         .collect::<Vec<_>>();
     assert_eq!(guardian_requests.len(), actions.len());
 
-    let policy = include_str!("../../src/guardian/node_repl_policy.md");
+    let policy = include_str!("../../assets/guardian/node_repl_policy.md");
     let first_guardian_thread = guardian_requests[0].body_json()["client_metadata"]["thread_id"]
         .as_str()
         .expect("Guardian reviewer thread id")