Classify permission instructions under the permissions namespace (#40295)

## What changed

- Change the permission prompt content kind from
  `generic.permissions_instructions` to `permissions.instructions`.
- Update request annotation tests to expect the new content kind.

GitOrigin-RevId: e1e39c74ac24668ac1f3467bb0cc1335a9408712

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

@@ -201,7 +201,7 @@ async fn first_request_item_types_roles_and_content_annotations() -> Result<()>
         .join("\n");
     insta::assert_snapshot!(items, @r#"
     message developer ["guardian.approved_action"]
-    message developer ["generic.developer_instructions","token_budget.context_window_guidance","generic.permissions_instructions","environments.instructions"]
+    message developer ["generic.developer_instructions","token_budget.context_window_guidance","permissions.instructions","environments.instructions"]
     message developer ["token_budget.context_window"]
     message developer ["multi_agent.usage_hint"]
     message developer ["multi_agent.mode_instructions"]

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

@@ -267,7 +267,7 @@ async fn token_budget_guidance_precedes_standalone_context_window() -> Result<()
     let request = response.single_request();
     assert!(request.has_content_kinds(&[
         "token_budget.context_window_guidance",
-        "generic.permissions_instructions",
+        "permissions.instructions",
     ]));
     assert!(request.has_content_kinds(&["token_budget.context_window"]));
     let developer_texts = request.message_input_texts("developer");

codex-rs/prompts/src/permissions_instructions.rs

@@ -179,7 +179,7 @@ impl ContextualUserFragment for PermissionsInstructions {
     }
 
     fn content_kind(&self) -> ContentItemKind {
-        ContentItemKind("generic.permissions_instructions".to_string())
+        ContentItemKind("permissions.instructions".to_string())
     }
 
     fn markers(&self) -> (&'static str, &'static str) {