* fix(config): preserve \$schema field across config rewrites
Add \$schema to the OpenClawConfig TypeScript type so it survives
the config write-back cycle. The Zod schema already accepted it
(added in #14998) but the TypeScript type omitted it, causing the
field to be silently stripped during config serialization.
Adds a round-trip test through validateConfigObject to prevent
regression.
Closes#43578
* fix(config): preserve root $schema during partial writes
* fix(config): preserve root $schema only when omitted
* fix(config): preserve root-authored $schema only
---------
Co-authored-by: Altay <altay@uinaf.dev>
a2eb8fa48f