Simple directory mentions (#14970)

- Adds simple support for directory mentions in the TUI.
- Codex App/VS Code will require minor change to recognize a directory
mention as such and change the link behavior.
- Directory mentions have a trailing slash to differentiate from
extensionless files


<img width="972" height="382" alt="image"
src="https://github.com/user-attachments/assets/8035b1eb-0978-465b-8d7a-4db2e5feca39"
/>
<img width="978" height="228" alt="image"
src="https://github.com/user-attachments/assets/af22cf0b-dd10-4440-9bee-a09915f6ba52"
/>

codex-rs/app-server-protocol/src/protocol/common.rs

@@ -800,11 +800,20 @@ pub struct FuzzyFileSearchParams {
 pub struct FuzzyFileSearchResult {
     pub root: String,
     pub path: String,
+    pub match_type: FuzzyFileSearchMatchType,
     pub file_name: String,
     pub score: u32,
     pub indices: Option<Vec<u32>>,
 }
 
+#[derive(Serialize, Deserialize, Debug, Clone, Copy, PartialEq, Eq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(rename_all = "camelCase")]
+pub enum FuzzyFileSearchMatchType {
+    File,
+    Directory,
+}
+
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
 pub struct FuzzyFileSearchResponse {
     pub files: Vec<FuzzyFileSearchResult>,