mark-related commands should work with existing structure

[yam655]

There's a difference with a new/unstructured song draft and an in-progress draft that is composed of a baseline set of known-good segments.

The normal mark/block-related commands need to work as expected with an established set of marks/blocks.

mark_good -> restart block: keep work mark_bad -> restart block: trash work next -> next block; keep work

Need new commands:

• block-flow through/end toggle (one block at a time or whole song?)
• previous -> previous block; trash work

Note: Right now there's no immediate need for a "block-repeat" mode (with the block-flow modes), as you still need to know whether you want to keep each pass, and the mark_good/mark_bad covers the general use-case.

Further note: "flow-through: end" mode may support "conditional approval" on the backend, allowing the segment to be replayed before it is accepted/rejected. "conditional-approval" marks the end of a file-unit allowing a "mark_good" or a "mark_bad" to be appended later without a reasonable time-code.

[yam655]

This ticket may become irrelevant before it is implemented.

The measure-based viewpoint works differently, the defined-by-voice approach makes this less effective as well.