[FEATURE]: expand shell.env hook context with messageID and agent

[micuintus]

• I've checked that this feature hasn't been suggested before.

TL;DR

Expand the shell.env plugin hook trigger in bash.ts to include messageID and agent in the context, so plugins know which message and agent triggered a bash command.

More detail

The Plugin.trigger("shell.env", ...) call in bash.ts currently passes minimal context. Plugins that need to set environment variables conditionally (e.g. only for agent-initiated commands, or per-message) have no way to know which message or agent triggered the shell invocation.

This change adds messageID and agent to the trigger context for the bash.ts call site only (the other call sites in prompt.ts and pty/index.ts are for user-initiated commands and are a separate concern).

Part of the plugin primitives work tracked in #20018 (split from #21687).

[github-actions]

This issue doesn't fully meet our contributing guidelines.

What needs to be fixed:

• The title should start with [FEATURE]: as required by the Feature Request template (e.g. [FEATURE]: expand shell.env hook context with messageID and agent)

Please edit this issue to address the above within 2 hours, or it will be automatically closed.

---

This issue might be a duplicate of existing issues. Please check:

• [FEATURE]: Add messageID to tool.execute.before/after hook payloads #15933: Also requests adding messageID to plugin hook payloads (tool.execute.before/after), same motivation of correlating hook calls to assistant messages
• [FEATURE]: surface parentAgent identity in plugin hook input #15403: Requests surfacing agent identity in plugin hook inputs including shell.env, overlapping with the agent part of this request

If you believe this was flagged incorrectly, please let a maintainer know.

[github-actions]

Thanks for updating the issue! It now follows the contributing guidelines and feature request template. The compliance label has been removed.