codex-tools: extract discoverable tool models (#16254)

## Why

`#16193` moved the pure `tool_search` and `tool_suggest` spec builders
into `codex-tools`, but `codex-core` still owned the shared
discoverable-tool model that those builders and the `tool_suggest`
runtime both depend on. This change continues the migration by moving
that reusable model boundary out of `codex-core` as well, so the
discovery/suggestion stack uses one shared set of types and
`core/src/tools` no longer needs its own `discoverable.rs` module.

## What changed

- Moved `DiscoverableTool`, `DiscoverablePluginInfo`, and
`filter_tool_suggest_discoverable_tools_for_client()` into
`codex-rs/tools/src/tool_discovery.rs` alongside the extracted
discovery/suggestion spec builders.
- Added `codex-app-server-protocol` as a `codex-tools` dependency so the
shared discoverable-tool model can own the connector-side `AppInfo`
variant directly.
- Updated `core/src/tools/handlers/tool_suggest.rs`,
`core/src/tools/spec.rs`, `core/src/tools/router.rs`,
`core/src/connectors.rs`, and `core/src/codex.rs` to consume the shared
`codex-tools` model instead of the old core-local declarations.
- Changed `core/src/plugins/discoverable.rs` to return
`DiscoverablePluginInfo` directly, moved the pure client-filter coverage
into `tool_discovery_tests.rs`, and deleted the old
`core/src/tools/discoverable.rs` module.
- Updated `codex-rs/tools/README.md` so the crate boundary documents
that `codex-tools` now owns the discoverable-tool models in addition to
the discovery/suggestion spec builders.

## Test plan

- `cargo test -p codex-tools`
- `CARGO_TARGET_DIR=/tmp/codex-core-discoverable-model cargo test -p
codex-core --lib tools::handlers::tool_suggest::`
- `CARGO_TARGET_DIR=/tmp/codex-core-discoverable-model cargo test -p
codex-core --lib tools::spec::`
- `CARGO_TARGET_DIR=/tmp/codex-core-discoverable-model cargo test -p
codex-core --lib plugins::discoverable::`
- `just bazel-lock-check`
- `just argument-comment-lint`

## References

- #16193
- #16154
- #15923
- #15928
- #15944
- #15953
- #16031
- #16047
- #16129
- #16132
- #16138
- #16141

codex-rs/core/src/plugins/discoverable.rs

@@ -9,6 +9,7 @@ use super::PluginsManager;
 use crate::config::Config;
 use crate::config::types::ToolSuggestDiscoverableType;
 use codex_features::Feature;
+use codex_tools::DiscoverablePluginInfo;
 
 const TOOL_SUGGEST_DISCOVERABLE_PLUGIN_ALLOWLIST: &[&str] = &[
     "github@openai-curated",
@@ -23,7 +24,7 @@ const TOOL_SUGGEST_DISCOVERABLE_PLUGIN_ALLOWLIST: &[&str] = &[
 
 pub(crate) fn list_tool_suggest_discoverable_plugins(
     config: &Config,
-) -> anyhow::Result<Vec<PluginCapabilitySummary>> {
+) -> anyhow::Result<Vec<DiscoverablePluginInfo>> {
     if !config.features.enabled(Feature::Plugins) {
         return Ok(Vec::new());
     }
@@ -47,7 +48,7 @@ pub(crate) fn list_tool_suggest_discoverable_plugins(
         return Ok(Vec::new());
     };
 
-    let mut discoverable_plugins = Vec::<PluginCapabilitySummary>::new();
+    let mut discoverable_plugins = Vec::<DiscoverablePluginInfo>::new();
     for plugin in curated_marketplace.plugins {
         if plugin.installed
             || (!TOOL_SUGGEST_DISCOVERABLE_PLUGIN_ALLOWLIST.contains(&plugin.id.as_str())
@@ -66,14 +67,28 @@ pub(crate) fn list_tool_suggest_discoverable_plugins(
                 marketplace_path: curated_marketplace.path.clone(),
             },
         ) {
-            Ok(plugin) => discoverable_plugins.push(plugin.plugin.into()),
+            Ok(plugin) => {
+                let plugin: PluginCapabilitySummary = plugin.plugin.into();
+                discoverable_plugins.push(DiscoverablePluginInfo {
+                    id: plugin.config_name,
+                    name: plugin.display_name,
+                    description: plugin.description,
+                    has_skills: plugin.has_skills,
+                    mcp_server_names: plugin.mcp_server_names,
+                    app_connector_ids: plugin
+                        .app_connector_ids
+                        .into_iter()
+                        .map(|connector_id| connector_id.0)
+                        .collect(),
+                });
+            }
             Err(err) => warn!("failed to load discoverable plugin suggestion {plugin_id}: {err:#}"),
         }
     }
     discoverable_plugins.sort_by(|left, right| {
-        left.display_name
-            .cmp(&right.display_name)
-            .then_with(|| left.config_name.cmp(&right.config_name))
+        left.name
+            .cmp(&right.name)
+            .then_with(|| left.id.cmp(&right.id))
     });
     Ok(discoverable_plugins)
 }

codex-rs/core/src/plugins/discoverable_tests.rs

@@ -5,7 +5,7 @@ use crate::plugins::test_support::write_curated_plugin_sha;
 use crate::plugins::test_support::write_file;
 use crate::plugins::test_support::write_openai_curated_marketplace;
 use crate::plugins::test_support::write_plugins_feature_config;
-use crate::tools::discoverable::DiscoverablePluginInfo;
+use codex_tools::DiscoverablePluginInfo;
 use codex_utils_absolute_path::AbsolutePathBuf;
 use pretty_assertions::assert_eq;
 use tempfile::tempdir;
@@ -18,11 +18,7 @@ async fn list_tool_suggest_discoverable_plugins_returns_uninstalled_curated_plug
     write_plugins_feature_config(codex_home.path());
 
     let config = load_plugins_config(codex_home.path()).await;
-    let discoverable_plugins = list_tool_suggest_discoverable_plugins(&config)
-        .unwrap()
-        .into_iter()
-        .map(DiscoverablePluginInfo::from)
-        .collect::<Vec<_>>();
+    let discoverable_plugins = list_tool_suggest_discoverable_plugins(&config).unwrap();
 
     assert_eq!(
         discoverable_plugins,
@@ -52,11 +48,7 @@ plugins = false
     );
 
     let config = load_plugins_config(codex_home.path()).await;
-    let discoverable_plugins = list_tool_suggest_discoverable_plugins(&config)
-        .unwrap()
-        .into_iter()
-        .map(DiscoverablePluginInfo::from)
-        .collect::<Vec<_>>();
+    let discoverable_plugins = list_tool_suggest_discoverable_plugins(&config).unwrap();
 
     assert_eq!(discoverable_plugins, Vec::<DiscoverablePluginInfo>::new());
 }
@@ -76,11 +68,7 @@ async fn list_tool_suggest_discoverable_plugins_normalizes_description() {
     );
 
     let config = load_plugins_config(codex_home.path()).await;
-    let discoverable_plugins = list_tool_suggest_discoverable_plugins(&config)
-        .unwrap()
-        .into_iter()
-        .map(DiscoverablePluginInfo::from)
-        .collect::<Vec<_>>();
+    let discoverable_plugins = list_tool_suggest_discoverable_plugins(&config).unwrap();
 
     assert_eq!(
         discoverable_plugins,
@@ -115,11 +103,7 @@ async fn list_tool_suggest_discoverable_plugins_omits_installed_curated_plugins(
         .expect("plugin should install");
 
     let refreshed_config = load_plugins_config(codex_home.path()).await;
-    let discoverable_plugins = list_tool_suggest_discoverable_plugins(&refreshed_config)
-        .unwrap()
-        .into_iter()
-        .map(DiscoverablePluginInfo::from)
-        .collect::<Vec<_>>();
+    let discoverable_plugins = list_tool_suggest_discoverable_plugins(&refreshed_config).unwrap();
 
     assert_eq!(discoverable_plugins, Vec::<DiscoverablePluginInfo>::new());
 }
@@ -140,11 +124,7 @@ discoverables = [{ type = "plugin", id = "sample@openai-curated" }]
     );
 
     let config = load_plugins_config(codex_home.path()).await;
-    let discoverable_plugins = list_tool_suggest_discoverable_plugins(&config)
-        .unwrap()
-        .into_iter()
-        .map(DiscoverablePluginInfo::from)
-        .collect::<Vec<_>>();
+    let discoverable_plugins = list_tool_suggest_discoverable_plugins(&config).unwrap();
 
     assert_eq!(
         discoverable_plugins,