Built /workspace/alknet-tty-poc against portable_pty 0.9 to validate the
local-PTY path (Step 2 of the build order) before Phase 1 specs. The POC
surfaced two constraints that were not knowable from reading the
portable_pty docs alone and that the architect must carry into the
tty-backend.md and tty-local.md specs:
- REQ-TTY-01: portable_pty is a blocking std::io API; the TtyBackend
trait must accommodate blocking backends that bridge to async via std
threads + tokio mpsc. exit_code resolves to a Future the adapter
awaits (resolves the load-bearing half of OQ-TTY-01).
- REQ-TTY-02: signal forwarding must target the process group
(kill(-pgid, sig)), which depends on the child being a session leader
(portable_pty's controlling_tty=true default).
The POC also validated the control channel (stream_type 3), JSON control
messages (DP-3), and exit-code-on-control-chunk (DP-5). OQ-TTY-01 is
marked resolved with the control-as-Clone-trait-object sub-question left
open with a POC-informed recommendation. The POC itself lives in the dev
workspace, not the repo; this doc is the durable record.
- alknet-ssh: remove paragraphs describing old hedging problem in channel
decomposition section and DP-4 — state the insight directly
- alknet-tty: replace 'defer for v1' / 'reserved for future use' with
'not needed for the current scope' in OQ-TTY-02
