feat: b5-config-validate — batch 5 wave 2

rust/crates/runtime/src/lib.rs

@@ -10,6 +10,7 @@ mod bootstrap;
 pub mod branch_lock;
 mod compact;
 mod config;
+pub mod config_validate;
 mod conversation;
 mod file_ops;
 pub mod green_contract;
@@ -53,6 +54,10 @@ pub use compact::{
     compact_session, estimate_session_tokens, format_compact_summary,
     get_compact_continuation_message, should_compact, CompactionConfig, CompactionResult,
 };
+pub use config_validate::{
+    check_unsupported_format, format_diagnostics, validate_config_file, ConfigDiagnostic,
+    DiagnosticKind, ValidationResult,
+};
 pub use config::{
     ConfigEntry, ConfigError, ConfigLoader, ConfigSource, McpConfigCollection,
     McpManagedProxyServerConfig, McpOAuthConfig, McpRemoteServerConfig, McpSdkServerConfig,