Expose MCP app identity in app context (#29934)

## Why

MCP tool-call events need to expose trusted app identity and action
metadata directly so v2 clients do not have to infer it from tool names
or resource URIs.

## What changed

- Add optional `appName`, `templateId`, and `actionName` fields to MCP
tool-call `appContext`.
- Populate `appName` and `templateId` from trusted Codex Apps metadata,
and derive `actionName` from the trusted app resource metadata.
- Preserve all three fields through core events, legacy protocol events,
persisted thread history, resume redaction, and app-server v2 responses.
- Document the public `appContext` fields in
`codex-rs/app-server/README.md`.
- Regenerate app-server JSON and TypeScript schemas and add coverage for
serialization, persistence, redaction, and metadata propagation.

## Validation

- `just test -p codex-app-server-protocol mcp_tool_call`
- `just test -p codex-core
mcp_tool_call_item_metadata_only_trusts_codex_apps_identity
mcp_tool_call_item_includes_app_identity`
- `just write-app-server-schema`

---------

Co-authored-by: Martin Au-Yeung <280153141+martinauyeung-oai@users.noreply.github.com>

codex-rs/core/tests/suite/rmcp_client.rs

@@ -1359,6 +1359,9 @@ async fn stdio_image_responses_round_trip() -> anyhow::Result<()> {
             connector_id: None,
             mcp_app_resource_uri: None,
             link_id: None,
+            app_name: None,
+            template_id: None,
+            action_name: None,
             plugin_id: None,
         },
     );

codex-rs/core/tests/suite/search_tool.rs

@@ -545,6 +545,8 @@ async fn tool_search_returns_deferred_tools_without_follow_up_tool_injection() -
         unreachable!("event guard guarantees McpToolCallBegin");
     };
     assert_eq!(begin.call_id, "calendar-call-1");
+    assert_eq!(begin.app_name.as_deref(), Some("Calendar"));
+    assert_eq!(begin.action_name.as_deref(), Some("calendar_create_event"));
     assert_eq!(
         begin.mcp_app_resource_uri.as_deref(),
         Some(CALENDAR_CREATE_EVENT_MCP_APP_RESOURCE_URI)
@@ -559,6 +561,8 @@ async fn tool_search_returns_deferred_tools_without_follow_up_tool_injection() -
     };
     assert_eq!(end.call_id, "calendar-call-1");
     assert_eq!(end.connector_id.as_deref(), Some("calendar"));
+    assert_eq!(end.app_name.as_deref(), Some("Calendar"));
+    assert_eq!(end.action_name.as_deref(), Some("calendar_create_event"));
     assert_eq!(
         end.mcp_app_resource_uri.as_deref(),
         Some(CALENDAR_CREATE_EVENT_MCP_APP_RESOURCE_URI)