Do bit-shifting in parents, not children.

[mrcslws]

Remove awareness of siblings from regions / encoders. Rather than returning a set of final indices, return a lazy seq of unshifted indices, allowing the caller to shift as needed.

[mrcslws]

Verified:

• The tests pass
• It's performance-neutral, according to the perf tests
• Each comportexviz demo seems to behave the same

I see that the encoders specifically handle nil, returning an empty set. So I continued this, returning an empty sequence. I haven't investigated whether this is necessary (i.e. whether we could just use (when ...) and return nil otherwise).

[mrcslws]

My .emacs is set to remove trailing whitespace on save, hence the whitespace-only changes. Let me know if I should avoid that (e.g. if our editor configs will get into a fight)

[floybix]

Good work! It's clear you grok the code.