procscope v0.3.0 — typed Options

Capture(kind string, debug int, seconds int) becomes Capture(Options), with
every axis a named type: Kind, Format, Detail, and Window as a time.Duration.

The debug integer is gone from the API. It conflated format with verbosity --
0 meant protobuf, higher meant text AND a detail level -- so it is now Format
plus Detail, and the pprof integer stays internal.

An unrecognised Kind/Format/Detail is now an error rather than a silent
fallback to heap, and FormatText is refused for cpu and trace, which have no
text form.

The package moves to the repo root: procscope.Capture(...).