Simplify package-based skill reads (#37808)

## What changed

- Make `package` the only required argument to `skills.read`, resolving the
  owning orchestrator or executor catalog automatically.
- Default omitted `resource` values to the package's main `SKILL.md`.
- Render orchestrator skills as package locators and instruct the model to read
  them directly without first calling `skills.list`.
- Update skill extension and app-server coverage for direct main-resource
  reads, referenced resources, aliases, and the revised tool schema.

GitOrigin-RevId: 9faf57a8d0935566a15094931eaabaa8f0613e9e

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

@@ -181,7 +181,13 @@ struct SkillLine<'a> {
 
 impl<'a> SkillLine<'a> {
     fn new(entry: &'a SkillCatalogEntry, policy: SkillCatalogRenderPolicy) -> Self {
-        Self::with_locator(entry, policy, entry.rendered_path().to_string())
+        let locator = match &entry.authority.kind {
+            SkillSourceKind::Orchestrator => entry.id.0.as_str(),
+            SkillSourceKind::Host | SkillSourceKind::Executor | SkillSourceKind::Custom(_) => {
+                entry.rendered_path()
+            }
+        };
+        Self::with_locator(entry, policy, locator.to_string())
     }
 
     fn with_locator(
@@ -197,7 +203,7 @@ impl<'a> SkillLine<'a> {
             locator_kind: match &entry.authority.kind {
                 SkillSourceKind::Host => "file",
                 SkillSourceKind::Executor => "environment resource",
-                SkillSourceKind::Orchestrator => "orchestrator resource",
+                SkillSourceKind::Orchestrator => "orchestrator package",
                 SkillSourceKind::Custom(_) => "custom resource",
             },
         }
@@ -1071,12 +1077,18 @@ fn build_alias_plan(entries: &[&SkillCatalogEntry]) -> Option<AliasPlan> {
 }
 
 fn render_skill_locator_with_aliases(entry: &SkillCatalogEntry, plan: &AliasPlan) -> String {
+    let locator = match &entry.authority.kind {
+        SkillSourceKind::Orchestrator => entry.id.0.as_str(),
+        SkillSourceKind::Host | SkillSourceKind::Executor | SkillSourceKind::Custom(_) => {
+            entry.rendered_path()
+        }
+    };
     if entry.alias_root().is_none() {
-        return entry.rendered_path().to_string();
+        return locator.to_string();
     }
-    let locator = entry.rendered_path().replace('\\', "/");
-    plan.shorten(&locator)
-        .unwrap_or_else(|| entry.rendered_path().to_string())
+    let normalized_locator = locator.replace('\\', "/");
+    plan.shorten(&normalized_locator)
+        .unwrap_or_else(|| locator.to_string())
 }
 
 fn aliased_metadata_overhead_cost(