Enable resource reads for explicit executor skills (#35198)

## Why

Executor skills that disallow implicit invocation are omitted from `skills.list`, so an explicitly selected skill did not provide the authority and package identifiers needed to read its referenced resources.

## What changed

- Add `resource_access` metadata to injected instructions for explicit-only executor skills.
- Teach the `skills.read` description to accept that metadata as well as values returned by `skills.list`.
- Keep discoverable executor skill instructions unchanged.

## Testing

Add an app-server integration scenario that selects an explicit-only executor skill, confirms it remains absent from `skills.list`, and reads a referenced file through `skills.read`.

GitOrigin-RevId: 97d3b93d1618c013363788452303c8a31e32cc56

codex-rs/ext/skills/src/extension.rs

@@ -36,6 +36,7 @@ use crate::catalog::SkillCatalogEntry;
 use crate::catalog::SkillReadResult;
 use crate::catalog::SkillSourceKind;
 use crate::fragments::AvailableSkillsInstructions;
+use crate::fragments::ExecutorSkillResourceAccess;
 use crate::fragments::SkillInstructions;
 use crate::provider::HostSkillProvider;
 use crate::provider::SkillListQuery;
@@ -464,6 +465,13 @@ where
                             )
                             .0,
                             contents,
+                            executor_resource_access: (!entry.prompt_visible
+                                && entry.authority.kind == SkillSourceKind::Executor)
+                                .then(|| ExecutorSkillResourceAccess {
+                                    authority_id: entry.authority.id.clone(),
+                                    package: entry.id.0.clone(),
+                                    main_resource: entry.main_prompt.as_str().to_string(),
+                                }),
                         };
                         fragments.push(Box::new(fragment));
                         main_prompts_injected = true;

codex-rs/ext/skills/src/fragments.rs

@@ -77,6 +77,14 @@ pub(crate) struct SkillInstructions {
     pub(crate) name: String,
     pub(crate) path: String,
     pub(crate) contents: String,
+    pub(crate) executor_resource_access: Option<ExecutorSkillResourceAccess>,
+}
+
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub(crate) struct ExecutorSkillResourceAccess {
+    pub(crate) authority_id: String,
+    pub(crate) package: String,
+    pub(crate) main_resource: String,
 }
 
 impl ContextualUserFragment for SkillInstructions {
@@ -96,6 +104,21 @@ impl ContextualUserFragment for SkillInstructions {
         let name = &self.name;
         let path = &self.path;
         let contents = &self.contents;
-        format!("\n<name>{name}</name>\n<path>{path}</path>\n{contents}\n")
+        let resource_access = self
+            .executor_resource_access
+            .as_ref()
+            .map(|access| {
+                let metadata = serde_json::json!({
+                    "authority": {
+                        "kind": "executor",
+                        "id": access.authority_id,
+                    },
+                    "package": access.package,
+                    "main_resource": access.main_resource,
+                });
+                format!("\n<resource_access>{metadata}</resource_access>")
+            })
+            .unwrap_or_default();
+        format!("\n<name>{name}</name>\n<path>{path}</path>{resource_access}\n{contents}\n")
     }
 }

codex-rs/ext/skills/src/tools/read.rs

@@ -56,7 +56,7 @@ impl ToolExecutor<ToolCall> for ReadTool {
     fn spec(&self) -> ToolSpec {
         skill_function_tool::<ReadArgs, ReadResponse>(
             TOOL_NAME,
-            "Read one page from a skill resource. Pass the exact authority and package from skills.list, plus its main_resource or a referenced resource beneath that package. Pass next_cursor back as cursor to continue.",
+            "Read one page from a skill resource. Pass the exact authority and package from skills.list or an explicitly selected skill's resource_access metadata, plus its main_resource or a referenced resource beneath that package. Pass next_cursor back as cursor to continue.",
         )
     }