[plugins] Inject remote_plugin_id into install elicitations (#26409)

Summary
- Propagate cached remote plugin IDs through Codex plugin discovery.
- Inject `remote_plugin_id` and connector IDs into
`request_plugin_install` elicitation `_meta` from the resolved plugin.
- Keep the remote plugin ID out of the model-facing tool schema,
arguments, and result.

Validation
- `just test -p codex-tools`
- `just test -p codex-core-plugins`
- `just test -p codex-core
list_tool_suggest_discoverable_plugins_includes_cached_remote_global_plugins`
- `just fix -p codex-tools`
- `just fix -p codex-core-plugins`
- `just fix -p codex-core`
- `git diff --check`
- `just test -p codex-core` was also attempted: 2,581 passed, 55 failed,
and 1 timed out across unrelated sandbox/environment-sensitive
integration tests.

codex-rs/tools/src/tool_discovery.rs

@@ -93,6 +93,7 @@ pub fn filter_request_plugin_install_discoverable_tools_for_client(
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub struct DiscoverablePluginInfo {
     pub id: String,
+    pub remote_plugin_id: Option<String>,
     pub name: String,
     pub description: Option<String>,
     pub has_skills: bool,