For ACP agents that need files in local filesystem for auth, add logic

secret -> file

in software-agent-sdk, this way in OpenHands/Canvas we just need to seed one secret to enable that, no need for special path https://github.com/OpenHands/software-agent-sdk/pull/3269 This can be generalized (to some extent) so that it works for general acp processes with slightly different file auth systems @chilly-france-44439

Actually i think in agent-canvas we do mount

~/.claude

~/codex

so we'd probably don't need this? 👀

I can be wrong but it seems claude code doesn't auth with any file (mac = keychain) but it can auth with secret

CLAUDE_CODE_OAUTH_TOKEN

IDK I think it simplifies a lot for Clients if we use a special env secret for ACP servers that require file auth

Replied here: https://openhands-ai.slack.com/archives/C06R25BT5B2/p1779114298956669?thread_ts=1779112142.304149&cid=C06R25BT5B2!