feat: disable capabilities by model provider (#19442)

## Why

Unsupported features must fail closed and Codex must not expose
OpenAI-hosted fallback paths when the active provider cannot support
them. In practice, Bedrock should not surface app connectors, MCP
servers, tool search/suggestions, image generation, web search, or JS
REPL until those paths are explicitly supported for that provider.

This PR moves that decision into provider-owned capability metadata
instead of scattering Bedrock-specific checks across callers.

## What changed

- Adds `ProviderCapabilities` to `codex-model-provider`, with default
support for existing providers and a Bedrock override that disables
unsupported launch surfaces.
- Adds `ToolCapabilityBounds` to `codex-tools` so provider capability
limits can clamp otherwise-enabled tool config.
- Applies capability bounds when building session and review-thread tool
config.
- Routes MCP/app connector configuration through
`McpManager::mcp_config`, which filters configured MCP servers and app
connectors based on the active provider.
- Updates app-server MCP list/read paths to use the filtered MCP config.
- Adds coverage for default provider capabilities, Bedrock disabled
capabilities, and optional tool-surface clamping.

## Testing

built locally and verified that bedrock responses api now return without
errors calling unsupported tools.

codex-rs/model-provider/src/provider.rs

@@ -19,6 +19,28 @@ use crate::auth::auth_manager_for_provider;
 use crate::auth::resolve_provider_auth;
 use crate::models_endpoint::OpenAiModelsEndpoint;
 
+/// Optional provider-backed features that Codex may expose at runtime.
+///
+/// These capabilities are a provider-owned upper bound. Callers can disable
+/// more functionality through normal config, but should not expose a feature
+/// that the active provider marks unsupported here.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct ProviderCapabilities {
+    pub namespace_tools: bool,
+    pub image_generation: bool,
+    pub web_search: bool,
+}
+
+impl Default for ProviderCapabilities {
+    fn default() -> Self {
+        Self {
+            namespace_tools: true,
+            image_generation: true,
+            web_search: true,
+        }
+    }
+}
+
 /// Current app-visible account state for a model provider.
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct ProviderAccountState {
@@ -59,6 +81,11 @@ pub trait ModelProvider: fmt::Debug + Send + Sync {
     /// Returns the configured provider metadata.
     fn info(&self) -> &ModelProviderInfo;
 
+    /// Returns the provider-owned capability upper bounds.
+    fn capabilities(&self) -> ProviderCapabilities {
+        ProviderCapabilities::default()
+    }
+
     /// Returns the provider-scoped auth manager, when this provider uses one.
     ///
     /// TODO(celia-oai): Make auth manager access internal to this crate so callers
@@ -301,6 +328,16 @@ mod tests {
         .expect("valid model")
     }
 
+    #[test]
+    fn configured_provider_uses_default_capabilities() {
+        let provider = create_model_provider(
+            ModelProviderInfo::create_openai_provider(/*base_url*/ None),
+            /*auth_manager*/ None,
+        );
+
+        assert_eq!(provider.capabilities(), ProviderCapabilities::default());
+    }
+
     #[test]
     fn create_model_provider_builds_command_auth_manager_without_base_manager() {
         let provider = create_model_provider(