[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/core-plugins/src/discoverable.rs

@@ -68,6 +68,7 @@ pub struct ToolSuggestPluginDiscoveryInput {
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub struct ToolSuggestDiscoverablePlugin {
     pub id: String,
+    pub remote_plugin_id: Option<String>,
     pub name: String,
     pub description: Option<String>,
     pub has_skills: bool,
@@ -162,6 +163,7 @@ impl PluginsManager {
 
                         discoverable_plugins.push(ToolSuggestDiscoverablePlugin {
                             id: plugin.config_name,
+                            remote_plugin_id: None,
                             name: plugin.display_name,
                             description: plugin.description,
                             has_skills: plugin.has_skills,
@@ -217,6 +219,7 @@ impl PluginsManager {
 
                 discoverable_plugins.push(ToolSuggestDiscoverablePlugin {
                     id: plugin.config_id,
+                    remote_plugin_id: Some(plugin.remote_plugin_id),
                     name: plugin.name,
                     description: plugin.description,
                     has_skills: plugin.has_skills,