[codex] Remove string-keyed MCP tool maps (#21454)

## Summary

This PR removes the synthetic `HashMap<String, ToolInfo>` keys from MCP
tool discovery. `McpConnectionManager::list_all_tools()` now returns
normalized `Vec<ToolInfo>`, and downstream code derives identity from
`ToolInfo::canonical_tool_name()`.

The motivation is to keep model-visible tool identity on
`ToolName`/`ToolInfo` instead of parallel string map keys, so future
namespace changes do not have to preserve otherwise-unused lookup keys.

## Changes

- Rename the MCP normalization path from `qualify_tools` to
`normalize_tools_for_model` and return tool values directly.
- Flow MCP tool lists through connectors, plugin injection, router/spec
building, code mode, and tool search as vectors/slices.
- Keep direct/deferred subtraction local to `mcp_tool_exposure`, using
`ToolName` values.
- Update tests to compare `ToolName` instances where MCP identity
matters.

## Validation

- `cargo test -p codex-mcp test_normalize_tools`
- `cargo test -p codex-core mcp_tool_exposure`
- `cargo test -p codex-core
direct_mcp_tools_register_namespaced_handlers`
- `cargo test -p codex-core
search_tool_registers_namespaced_mcp_tool_aliases`
- `just fix -p codex-mcp`
- `just fix -p codex-core`

codex-rs/codex-mcp/src/connection_manager.rs

@@ -34,7 +34,7 @@ use crate::server::EffectiveMcpServer;
 use crate::server::McpServerMetadata;
 use crate::tools::ToolInfo;
 use crate::tools::filter_tools;
-use crate::tools::qualify_tools;
+use crate::tools::normalize_tools_for_model;
 use crate::tools::tool_with_model_visible_input_schema;
 use anyhow::Context;
 use anyhow::Result;
@@ -363,10 +363,9 @@ impl McpConnectionManager {
         failures
     }
 
-    /// Returns a single map that contains all tools. Each key is the
-    /// fully-qualified name for the tool.
+    /// Returns all tools with model-visible names normalized.
     #[instrument(level = "trace", skip_all)]
-    pub async fn list_all_tools(&self) -> HashMap<String, ToolInfo> {
+    pub async fn list_all_tools(&self) -> Vec<ToolInfo> {
         let mut tools = Vec::new();
         for managed_client in self.clients.values() {
             let Some(server_tools) = managed_client.listed_tools().await else {
@@ -374,15 +373,15 @@ impl McpConnectionManager {
             };
             tools.extend(server_tools);
         }
-        qualify_tools(tools)
+        normalize_tools_for_model(tools)
     }
 
     /// Force-refresh codex apps tools by bypassing the in-process cache.
     ///
     /// On success, the refreshed tools replace the cache contents and the
-    /// latest filtered tool map is returned directly to the caller. On
+    /// latest filtered tools are returned directly to the caller. On
     /// failure, the existing cache remains unchanged.
-    pub async fn hard_refresh_codex_apps_tools_cache(&self) -> Result<HashMap<String, ToolInfo>> {
+    pub async fn hard_refresh_codex_apps_tools_cache(&self) -> Result<Vec<ToolInfo>> {
         let managed_client = self
             .clients
             .get(CODEX_APPS_MCP_SERVER_NAME)
@@ -425,7 +424,7 @@ impl McpConnectionManager {
                 tool.tool = tool_with_model_visible_input_schema(&tool.tool);
                 tool
             });
-        Ok(qualify_tools(tools))
+        Ok(normalize_tools_for_model(tools))
     }
 
     /// Returns a single map that contains all resources. Each key is the
@@ -664,7 +663,7 @@ impl McpConnectionManager {
     pub async fn resolve_tool_info(&self, tool_name: &ToolName) -> Option<ToolInfo> {
         let all_tools = self.list_all_tools().await;
         all_tools
-            .into_values()
+            .into_iter()
             .find(|tool| tool.canonical_tool_name() == *tool_name)
     }