Support portable Agent Plugins throughout installation (#36544)

## Why

Agent Plugins use a schema-declared root `plugin.json` and can have dotted names or versions that do not fit Codex's directory-safe version format. The packaging and installation paths still assumed the legacy manifest layout and identifier rules.

## What changed

- Recognize valid root Agent Plugin manifests when discovering, packing, and installing plugins, while leaving unrelated root manifests on the legacy path.
- Accept safe dotted plugin names, default missing Agent Plugin versions to `1.0.0`, and derive stable directory-safe versions when necessary without rewriting the portable manifest.
- Skip legacy command migration for Agent Plugins and reject symlinks or other unsupported file types while copying plugin sources.

## Testing

Add coverage for portable bundle round trips, manifest discovery, dotted names, version handling, command preservation, and symlink rejection.

GitOrigin-RevId: 61476c4c4100495842253d8b429c0b896490962d

codex-rs/plugin/src/plugin_id.rs

@@ -52,13 +52,32 @@ pub fn validate_plugin_segment(segment: &str, kind: &str) -> Result<(), String>
     if segment.is_empty() {
         return Err(format!("invalid {kind}: must not be empty"));
     }
-    if !segment
-        .chars()
-        .all(|ch| ch.is_ascii_alphanumeric() || ch == '-' || ch == '_')
+    let allow_dots = kind == "plugin name";
+    if allow_dots && matches!(segment, "." | "..") {
+        return Err(format!("invalid {kind}: path traversal is not allowed"));
+    }
+    if allow_dots && (segment.starts_with('.') || segment.ends_with('.') || segment.contains(".."))
     {
         return Err(format!(
-            "invalid {kind}: only ASCII letters, digits, `_`, and `-` are allowed"
+            "invalid {kind}: dots must separate non-empty name segments"
+        ));
+    }
+    if !segment
+        .chars()
+        .all(|ch| ch.is_ascii_alphanumeric() || matches!(ch, '-' | '_') || allow_dots && ch == '.')
+    {
+        let allowed_characters = if allow_dots {
+            "ASCII letters, digits, `.`, `_`, and `-`"
+        } else {
+            "ASCII letters, digits, `_`, and `-`"
+        };
+        return Err(format!(
+            "invalid {kind}: only {allowed_characters} are allowed"
         ));
     }
     Ok(())
 }
+
+#[cfg(test)]
+#[path = "plugin_id_tests.rs"]
+mod tests;

codex-rs/plugin/src/plugin_id_tests.rs

@@ -0,0 +1,34 @@
+use super::PluginId;
+
+#[test]
+fn accepts_dotted_plugin_names() {
+    let plugin_id =
+        PluginId::new("acme.tools".to_string(), "marketplace".to_string()).expect("plugin id");
+
+    assert_eq!(plugin_id.as_key(), "acme.tools@marketplace");
+}
+
+#[test]
+fn marketplace_names_preserve_legacy_character_set() {
+    PluginId::new("acme".to_string(), "marketplace_name-1".to_string()).expect("marketplace name");
+
+    let err = PluginId::new("acme".to_string(), "market.place".to_string())
+        .expect_err("dotted marketplace name");
+    assert_eq!(
+        err.to_string(),
+        "invalid marketplace name: only ASCII letters, digits, `_`, and `-` are allowed"
+    );
+}
+
+#[test]
+fn rejects_dot_path_segments() {
+    assert!(PluginId::new(".".to_string(), "marketplace".to_string()).is_err());
+    assert!(PluginId::new("plugin".to_string(), "..".to_string()).is_err());
+}
+
+#[test]
+fn rejects_dots_that_can_alias_path_segments() {
+    for plugin_name in [".plugin", "plugin.", "plugin..name"] {
+        assert!(PluginId::new(plugin_name.to_string(), "marketplace".to_string()).is_err());
+    }
+}