Add `FrozenProcessLocal` for immutable coordinator snapshots while
retaining the existing default wire-encoding rejection.
Prevent callers and msgspec config from replacing or omitting the
process-local sentinel. Wrap subclass validation hooks with base
checks so mutable and frozen structs cannot reopen the wire bypass.
Cover direct and nested encoding, shallow frozen behavior, sentinel
replacement, omitted defaults and hostile validation hooks.
Prompt-IO: ai/prompt-io/opencode/20260907T011533Z_5966e8aa_frozen_process_local.md
(this patch was generated in some part by `opencode` using `gpt-5.6-sol` (`openai`))
Gud Boi
d2274d3252