feat: add Devin spawn support

[m1kekad0]

Summary

Add native spawn support for the devin agent type.

This is a follow-up to the initial Devin agent-type integration and keeps the change intentionally narrow: no core spawn logic changes, no monitor support, and no Devin-specific branching.

Why

The initial Devin integration left spawn disabled because the required interactive boot mode had not yet been verified.

Devin CLI 3000.4.25 documents and supports:

devin [OPTIONS] [-- <PROMPT>...]

where the prompt starts an interactive session, while -p/--print is explicitly the non-interactive one-shot mode.

Verified locally:

devin -- "/agmsg actas devin-poc-test"

This successfully:

• processed the initial actas prompt
• remained in an interactive session
• accepted a second turn
• ran in the target project context

That satisfies agmsg's native spawn requirements.

What changes

Update the Devin manifest with:

spawnable=yes
prompt_arg=--
model_arg=--model

This lets the existing manifest-driven spawn path generate commands such as:

devin -- "/agmsg actas worker"

and, with a model:

devin --model claude-sonnet-4 -- "/agmsg actas worker"

No Devin-specific code is added to spawn.sh or the core boot-command logic.

Tests

Updated the existing spawn/type-registry coverage to verify:

• Devin is included in the spawnable set
• prompt_arg=-- is read from the manifest
• model_arg=--model is read from the manifest
• the generated command uses -- before the initial prompt
• the prompt is not passed as an invalid bare positional argument
• --model <id> is placed before the -- separator

Local verification:

• npm test — PASS
• Node.js test suite — PASS
• type registry tests — PASS
• spawn tests — PASS
• PTY smoke test with a real Devin CLI session — PASS

Documentation

The README spawnable count is updated from 8/10 to 9/10, and devin is added to the spawnable list.

The Hermes limitation and its reference to fujibee#279 remain unchanged.

Scope

Included:

• native Devin spawn support
• model forwarding
• spawn/type-registry tests
• README spawnable-count updates

Not included:

• monitor / automatic delivery
• Devin-specific TUI state detection
• Node launcher support
• Devin API integration
• resume/session orchestration
• core spawn refactoring

The implementation stays entirely within the existing manifest-driven architecture.

AI-assisted-by: Gemini 3.7 Flash