feat: add Devin agent type

[m1kekad0]

Summary

Add first-class devin agent type support for Devin CLI.

This PR adds Devin as a bundled agmsg agent type so it can join teams, resolve its identity independently from other agent types, and participate in manual agmsg messaging through the existing join / whoami / inbox / send flow.

I verified the integration against a locally installed Devin CLI before implementing the bundled type.

Why

Before this change, Devin could already access the local agmsg installation and use the messaging scripts, but it had to register under an existing agent type such as opencode.

That creates an identity collision when another agent of the same type is registered for the same project. For example:

multiple=true agents=DeepSeek,devin teams=poc type=opencode project=/path/to/project

Giving Devin its own agent_type=devin makes (project_path, agent_type) resolve uniquely without pretending to be another runtime.

What changes

Adds a bundled scripts/drivers/types/devin/ implementation with:

• type.conf
  • name=devin
  • cli=devin
  • detect_proc=devin devin-*
  • monitor=no
  • delivery_modes=off
• _delivery.sh
  • keeps Devin on manual delivery only
  • avoids touching another agent type's watcher when delivery is disabled
• template.md
  • uses the standard agmsg scripts for identity, join, inbox, send, history, team, config, and related commands
  • identifies itself with whoami.sh "$(pwd)" devin

The installer, supported-agent documentation, site metadata, and registry/delivery tests are updated accordingly.

Verified locally

The integration was exercised through the normal installed agmsg path, not by editing ~/.agents/skills/agmsg directly.

join.sh poc devin devin <project>
  -> Joined team poc as devin

whoami.sh <project> devin
  -> agent=devin teams=poc type=devin project=<project>

whoami.sh <project> opencode
  -> agent=DeepSeek teams=poc type=opencode project=<project>

Message exchange was also verified in both directions:

Claude -> Devin
Devin  -> Claude

using the existing send.sh / inbox.sh flow.

Tests

Verified locally:

• npm test
• Node test suite
• agent type registry tests
• delivery tests
• devin join / whoami identity resolution
• coexistence of opencode and devin in the same project
• manual send / inbox messaging

Scope

This PR deliberately keeps Devin on manual delivery:

delivery_modes=off
monitor=no

It does not add:

• automatic delivery / monitor hooks
• automatic session management
• Devin-specific TUI state detection
• spawn support (spawn support is intentionally deferred to a follow-up)

Devin is currently not marked spawnable because an interactive boot mode that can be pre-seeded with agmsg's initial actas prompt has not yet been verified. That is separate from the known Hermes limitation tracked in #279 and can be investigated independently.

The goal of this PR is the smallest first-class integration that is already verified end-to-end: identity, team membership, and manual cross-agent messaging.

AI-assisted-by: Gemini 3.7 Flash

[m1kekad0]

@fujibee
I noticed the contribution guide after opening this PR.

If you would prefer an issue-first discussion for adding a bundled agent type, I'm happy to open an issue and continue the design discussion there.

Otherwise, I'll keep this PR focused on the Devin agent-type integration and address any review feedback here.