feat: add Devin ACP provider support

[nkowne63]

Summary

• add Devin ACP as an external-process model provider
• wire Devin ACP into provider discovery, auth/status reporting, runtime resolution, setup/model switching, and delegation override validation
• add tests covering Devin ACP provider registration and credential/status behavior

Validation

• venv/bin/python -m pytest tests/hermes_cli/test_api_key_providers.py -q → 171 passed, 3 warnings
• venv/bin/hermes chat -q 'Reply with exactly OK and nothing else.' --provider devin-acp --ignore-user-config --source tool -Q → OK

Notes

This replaces the earlier oversized PR that was accidentally based on an old/stacked branch. This branch is rebuilt directly on the synced fork main / upstream origin/main and contains only the Devin ACP provider change.

[github-actions]

🔎 Lint report: codex/devin-acp-clean vs origin/main

ruff

Total: 0 on HEAD, 0 on base (➖ 0)

🆕 New issues: none

✅ Fixed issues: none

Unchanged: 0 pre-existing issues carried over.

ty (type checker)

Total: 11458 on HEAD, 11455 on base (🆕 +3)

🆕 New issues (3):

Rule	Count
unresolved-attribute	2
invalid-method-override	1

First entries

tests/run_agent/test_credits_notices_toggle.py:76: [unresolved-attribute] unresolved-attribute: Unresolved attribute `_credits_session_start_micros` on type `AIAgent`
run_agent.py:3002: [unresolved-attribute] unresolved-attribute: Object of type `Self@get_credits_spent_micros` has no attribute `_credits_session_start_micros`
plugins/model-providers/devin-acp/__init__.py:15: [invalid-method-override] invalid-method-override: Invalid override of method `fetch_models`: Definition is incompatible with `ProviderProfile.fetch_models`

✅ Fixed issues (1):

Rule	Count
invalid-assignment	1

First entries

tests/run_agent/test_credits_notices_toggle.py:76: [invalid-assignment] invalid-assignment: Object of type `None` is not assignable to attribute `_credits_session_start_micros` of type `int`

Unchanged: 6014 pre-existing issues carried over.

Diagnostics are surfaced as warnings — this check never fails the build.