Enrich V2 capability discovery with resolved plugin and skill metadata (#53763)

## What changed

- Return qualified skill names such as `team:deploy` and parsed `dependencies` and `policy` instead of a separate namespace and raw metadata file. Share `agents/openai.yaml` parsing and validation between skill loaders and executor discovery.
- Include each standalone skill's search-root ID and path in `discoveryRoot`, while accepting responses from older executors that omit it.
- Add plugin `displayName`, falling back to the manifest name or installation directory.
- Materialize inline MCP declarations in `mcpConfig` with the manifest as their source path, and report incomplete discovery when declared MCP or Apps configuration files have no returned contents.

## Testing

Add coverage for JSON round trips, omitted `discoveryRoot`, optional and invalid skill metadata, qualified names, display-name fallbacks, and inline MCP configuration. Verify standalone search roots survive cached discovery and sandboxed RPC responses.

GitOrigin-RevId: 4124972444ad7c2fb8c6418acbf9a589d797fad2

codex-rs/exec-server-protocol/src/capabilities.rs

@@ -1,13 +1,14 @@
 //! Executor capability inventory; callers apply identity and enablement.
 
 use codex_file_system::FileSystemSandboxContext;
+use codex_skills::SkillDependencies;
+use codex_skills::SkillPolicy;
 use codex_utils_path_uri::PathUri;
 use serde::Deserialize;
 use serde::Serialize;
 use std::fmt;
 use std::sync::Arc;
 
-use crate::CapabilityTextFile;
 use crate::DiscoveredPluginFiles;
 
 pub const CAPABILITIES_DISCOVER_V2_METHOD: &str = "capabilities/discoverV2";
@@ -44,6 +45,8 @@ pub struct DiscoverV2CapabilitiesResponse {
 pub struct ExecutorPlugin {
     /// Environment-local ID: `<name>@<marketplace>`.
     pub id: String,
+    /// Manifest display name, falling back to its name or the installation directory.
+    pub display_name: String,
     pub remote_plugin_id: Option<String>,
     pub version: String,
     pub root: PathUri,
@@ -51,20 +54,30 @@ pub struct ExecutorPlugin {
     pub skills: Vec<ExecutorSkill>,
 }
 
+/// Executor-owned search root for a standalone skill.
+#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct SkillDiscoveryRoot {
+    pub id: String,
+    pub path: PathUri,
+}
+
 /// Skill metadata, excluding instructions and resources.
 #[derive(Clone, PartialEq, Eq, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]
 pub struct ExecutorSkill {
+    /// Final skill name, qualified by the nearest enclosing plugin namespace when present.
     pub name: String,
-    /// Nearest enclosing legacy plugin's name, following V1 precedence.
-    #[serde(default)]
-    pub namespace: Option<String>,
     pub description: String,
     #[serde(default)]
     pub short_description: Option<String>,
     /// Path to SKILL.md, not its containing directory.
     pub path: PathUri,
-    pub metadata: Option<CapabilityTextFile>,
+    /// Absent for plugin skills and responses from older executors.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub discovery_root: Option<SkillDiscoveryRoot>,
+    pub dependencies: Option<SkillDependencies>,
+    pub policy: Option<SkillPolicy>,
 }
 
 impl fmt::Debug for ExecutorPlugin {
@@ -95,12 +108,7 @@ impl fmt::Debug for ExecutorSkill {
         formatter
             .debug_struct("ExecutorSkill")
             .field("name", &self.name)
-            .field("namespace", &self.namespace)
             .field("path", &self.path)
-            .field(
-                "metadata_path",
-                &self.metadata.as_ref().map(|file| &file.path),
-            )
             .finish()
     }
 }