## Unified PTY-Based Exec Tool
Note: this requires to have this flag in the config:
`use_experimental_unified_exec_tool=true`
- Adds a PTY-backed interactive exec feature (“unified_exec”) with
session reuse via
session_id, bounded output (128 KiB), and timeout clamping (≤ 60 s).
- Protocol: introduces ResponseItem::UnifiedExec { session_id,
arguments, timeout_ms }.
- Tools: exposes unified_exec as a function tool (Responses API);
excluded from Chat
Completions payload while still supported in tool lists.
- Path handling: resolves commands via PATH (or explicit paths), with
UTF‑8/newline‑aware
truncation (truncate_middle).
- Tests: cover command parsing, path resolution, session
persistence/cleanup, multi‑session
isolation, timeouts, and truncation behavior.
The `SessionManager` in `exec_command` owns a number of
`ExecCommandSession` objects where `ExecCommandSession` has a
non-trivial implementation of `Drop`, so we want to be able to drop an
individual `SessionManager` to help ensure things get cleaned up in a
timely fashion. To that end, we should have one `SessionManager` per
session rather than one global one for the lifetime of the CLI process.
