Separate serializable `BindspaceSpec` and `BindspaceIdentity` values
from a process-local `BindspaceHandle` carrying FD and ownership
authority.
Deats,
- add global `ProcessLocal` wire guards for local handle structs
- derive valid kinds and ownership from their `Literal` aliases
- require a positive inode while keeping the mutable name optional
- pin supplied FDs to identity inodes with `fstat()`
- cover round trips, nested encoding and stale capabilities
Caught-during: review remediation
Found-via: `/run-tests` test_bindspace_handle_pins_local_capability
Prompt-IO: ai/prompt-io/opencode/20260822T042026Z_29141f0b_prompt_io.md
(this patch was generated in some part by `opencode` using `gpt-5.6-sol` (`openai`))
Gud Boi