Adapt TUI terminal session & frame engine from grok-build for Rust CLI #68

Completed in commit e2da9bc051. Adapted BoxFrame TUI layout, border styling, header and status widgets using ratatui / crossterm.

Reopening for the PTY half. The box frame landed; the subprocess streaming did not.

Audited against 468f1fa325.

Met: crates/openagents-cli/src/tui.rs (59 lines) renders a BoxFrame with a header, a transcript paragraph, and a status footer, under ratatui + crossterm. That is a real, if minimal, frame.

Unmet, verbatim from this issue's scope: "Connect PTY and subprocess streaming for agent execution."

There is no PTY anywhere in the crate.

$ grep -rn "portable-pty\|openpty\|PtyPair\|pty" crates/openagents-cli/Cargo.toml
(no output)

crates/openagents-cli/Cargo.toml lists no PTY dependency — the ptyctl work this issue names from grok-build was not adapted. No subprocess output is streamed into the TUI either: the only place the crate spawns a child is delegate.rs, which uses buffered cmd.output() (delegate.rs:104, :116, :128, :140) and is not connected to the TUI at all. interactive.rs:15 discards the token as _token and never calls the runtime, so nothing streams into the frame from any source.

Also unmet: "the signature OpenAgents Coder box frame & interactive session view". The frame exists; the interactive session view does not — the event loop discards every keystroke. That half is tracked in #73, which is reopened and being rebuilt.

Acceptance for the reopen:

1. A child process runs under a PTY and its output renders live inside the box frame. Show the run.
2. A program that requires a TTY (for example top or a coloured git log) renders correctly, proving it is a PTY and not a pipe.
3. Resizing the terminal propagates the new size to the child.

Partial progress in c8d2f76040 (main, WAL receipt seq=181). Staying open.

Landed: the text-editing half of the adaptation. grok-build's xai-ratatui-textarea is ported into crates/openagents-cli/src/composer/ with its Apache-2.0 license vendored beside it, and the interactive session view renders in the OpenAgents frame rather than grok's. Raw-mode key handling is real -- the previous interactive.rs was 77 lines that dropped every key except Esc, q, and Tab.

Still missing from the scope above:

• PTY and subprocess streaming for agent execution. This is the substantive remainder. Nothing from ptyctl is adapted; the crate has no pty dependency and spawns no child under a terminal. Streaming today is HTTP chunks from the inference proxy, which is a different thing from running a subprocess under a pty and rendering its output.
• Binary texture splash.
• The broader frame-rendering component set from xai-grok-tui-components beyond what the composer needed.

Worth noting for whoever picks up the pty work: #85 and #70 (child delegation, parallel fan-out) need subprocess streaming too, and #84 needs it for shell tool execution. Doing pty once, here, is better than three lanes each growing their own.

Done in 43c92585c6. The remaining item was PTY and subprocess streaming, and it is built.

src/pty.rs adapts ptyctl over portable-pty + vt100: /run <command>, output rendered cell-for-cell with colour and attributes, resize reaching the child as SIGWINCH, keys encoded as a terminal would encode them, and Ctrl+] to detach.

The proof it is a real terminal and not a pipe is in the output — git printing (HEAD), a decoration it only emits when it believes stdout is a terminal:

Run · git --no-pager log --oneline -n 4 · finished
c6e7c8a940 (HEAD) Make ACP discovery only report actually-installed agents.

The composer half landed earlier (c8d2f76040): grok-build's xai-ratatui-textarea with its Apache-2.0 licence vendored beside it, rendered in the OpenAgents frame rather than grok's.

Worth flagging for whoever needs subprocess streaming next: PtyControl is a trait and pty.rs is shaped to be reused, but only /run is wired. #85, #70, and #84 all want it too, and tools.rs/delegate.rs were other agents' files during this pass. Doing pty once, here, is still the right shape.

Not done: the binary texture splash, and the wider xai-grok-tui-components set beyond what the panes needed. PTY tests use tty, stty size, cursor addressing and cat rather than a real top/vim — deterministic and CI-safe; the SIGWINCH test does trap a real signal in a real shell and is the most timing-dependent of them.