Use Duration strings instead of seconds when we accept timeouts / intervals

[ammario]

E.g., in coder_app and coder_agent.metadata.

[matifali]

Something like? 1m30s instead of 90?

[ammario]

Yes, exactly. It's not clear what the unit is otherwise.

It's also painful to write automated tests when the interval is 1s. It takes many seconds to get a significant sample size.

[ammario]

One reason to keep it a number is it simplifies arithmetic. I would still prefer we use milliseconds for testing and flexibility. Any key that accepts a duration number should indicate the unit in the suffix. E.g. we should use internal_ms instead of interval.