[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_tests.rs

@@ -37,6 +37,7 @@ fn filter_request_plugin_install_discoverable_tools_for_codex_tui_omits_plugins(
         })),
         DiscoverableTool::Plugin(Box::new(DiscoverablePluginInfo {
             id: "slack@openai-curated".to_string(),
+            remote_plugin_id: None,
             name: "Slack".to_string(),
             description: Some("Search Slack messages".to_string()),
             has_skills: true,