Time mistaken for a unit

`5:30pm` is spoken as "5 colon, 30 pico-metres"

The MathML is:
```

```
or potentially
```

```

There is a `time` intent property, but there is not any rule yet to handle it. I think the intent is needed. While "5:30pm" should be interpreted as time due to the `:`, the problem is still there for "5pm" (and "5am" -- arcminutes).

Start by tracing how the `time` intent property and the two MathML forms are currently handled. Add handling that keeps `5:30pm` as time and distinguishes `5pm` from unit interpretations, then verify the resulting speech for the examples in the issue.

Written by the indexing model from the issue text.