[Python] Set default value for ephemeral parameter in log_message method to False

[brettcannon]

Also narrow the parameter's type along the way.

[Copilot]

Pull request overview

Updates the Python SDK’s CopilotSession.log() API to make ephemeral default to False (and narrows its type), while also adjusting the method’s docstring.

Changes:

• Set CopilotSession.log(..., ephemeral=...) default from None to False and narrow the parameter type to bool.
• Update log() docstring text describing defaults for level and ephemeral.

[SteveSandersonMS]

@brettcannon This changes the semantics a bit. Previously we could differentiate "false" and "not set", but we'd lose that distinction with this change.

I think we'd be better off documenting the behavior as "If the flag is not set, the underlying runtime applies its own rules to control whether the log message is ephemeral".

For example we might want info-level messages to be ephemeral and errors not to be ephemeral, or to use other runtime conditions to decide.

All the other languages are consistent with this too, except for Go which actually fails to send "false" values at all from this API. I'm fixing Go separately in #827

[brettcannon]

I think we'd be better off documenting the behavior as "If the flag is not set, the underlying runtime applies its own rules to control whether the log message is ephemeral".

SGTM! I'll close this PR.