View in plain text option

All zets are rendered using glow

Should make it optional to view/output as plain text so it can be piped to other processes easily.

This might require changes to the interactive selector, potentially removing that for plain text meaning we only allow the directory timestamp as the arg passed to `zet view plain ` or something like that.

Start with the `zet view` command and the interactive selector, then trace how `glow` is used for rendering. The work is done when users can select plain-text output, including a usable `zet view plain ` form if appropriate, and pipe the result to other processes without terminal rendering.

Written by the indexing model from the issue text.