fix(config): add resolved field to ConfigFileSnapshot for pre-defaults config

The initial fix using snapshot.parsed broke configs with $include directives.
This commit adds a new 'resolved' field to ConfigFileSnapshot that contains
the config after $include and ${ENV} substitution but BEFORE runtime defaults
are applied. This is now used by config set/unset to avoid:
1. Breaking configs with $include directives
2. Leaking runtime defaults into the written config file

Also removes applyModelDefaults from writeConfigFile since runtime defaults
should only be applied when loading, not when writing.

src/config/types.openclaw.ts

@@ -114,6 +114,12 @@ export type ConfigFileSnapshot = {
   exists: boolean;
   raw: string | null;
   parsed: unknown;
+  /**
+   * Config after $include resolution and ${ENV} substitution, but BEFORE runtime
+   * defaults are applied. Use this for config set/unset operations to avoid
+   * leaking runtime defaults into the written config file.
+   */
+  resolved: OpenClawConfig;
   valid: boolean;
   config: OpenClawConfig;
   hash?: string;