[FEATURE] Include pid/pgid in terminal_info ACP metadata for orphan process detection

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

Agent terminals in Zed are display-only. When Claude Code runs a terminal command, Zed gets the output streamed through ACP ToolCall._meta (terminal_info, terminal_output, terminal_exit), but there's no actual process handle on Zed's side.

The problem: if a command spawns child processes that outlive the shell, Zed can't detect or kill them. Right now terminal_info only has terminal_id and cwd.
Without pid/pgid, there's no way to call killpg() after the shell exits.

I dug into this on the Zed side and confirmed there's nothing we can do without process group info from Claude Code.

Related Zed issue: https://github.com/zed-industries/zed/issues/51455

Proposed Solution

Add pid and pgid to the terminal_info metadata Claude Code already sends. Claude Code knows the shell's PID when it spawns it, so this is two extra fields in
existing JSON.

Current:
{"terminal_info": {"terminal_id": "toolu_...", "cwd": "/some/path"}}

With this change:
{"terminal_info": {"terminal_id": "toolu_...", "cwd": "/some/path", "pid": 12345, "pgid": 12345}}

_meta is freeform JSON, so no ACP protocol changes are needed.

Alternative Solutions

• A reverse terminal/kill in the ACP protocol (client-to-agent direction). Works, but that's a protocol-level change on both sides for what could be two JSON

fields.

• Scanning /proc by command string. Too fragile, too many false positives.

Priority

Critical - Blocking my work

Feature Category

CLI commands and flags

Use Case Example

1. User starts an agent session in Zed
2. Claude Code runs something that forks background workers (build script with watchers, dev server, etc.)
3. Shell exits with 0, Claude Code sends terminal_exit
4. Child processes keep running, consuming resources, no parent
5. Zed can't touch them because it has no PID or PGID
6. With pid/pgid in terminal_info, Zed calls killpg(pgid, 0) after exit, finds the orphans, and cleans up with SIGTERM

Additional Context

I traced through the Zed code that handles this. The parsing lives at crates/agent_servers/src/acp.rs where terminal_info is already extracted from _meta. Once Claude Code starts sending pid/pgid, the Zed side is a small patch.